Merge pull request #97 from cjwatson/flake8

Add a tox lint environment, and make it pass

19 files changed, 310 insertions, 195 deletions

diff --git a/.coveragerc b/.coveragerc
index 953ece6..617e435 100644
--- a/.coveragerc
+++ b/.coveragerc
@@ -1,4 +1,5 @@
 [run]
+plugins = coverage_python_version
 source = zope.schema
 
 [report]
diff --git a/src/zope/schema/_bootstrapfields.py b/src/zope/schema/_bootstrapfields.py
index 9a64a2d..6f2906b 100644
--- a/src/zope/schema/_bootstrapfields.py
+++ b/src/zope/schema/_bootstrapfields.py
@@ -62,7 +62,7 @@ from zope.schema._compat import PY2
 
 class _NotGiven(object):
 
-    def __repr__(self): # pragma: no cover
+    def __repr__(self):  # pragma: no cover
         return "<Not Given>"
 
 
@@ -77,7 +77,10 @@ class ValidatedProperty(object):
         self._allow_none = allow_none
 
     def __set__(self, inst, value):
-        bypass_validation = (value is None and self._allow_none) or value == inst.missing_value
+        bypass_validation = (
+            (value is None and self._allow_none)
+            or value == inst.missing_value
+        )
         if not bypass_validation:
             if self._check is not None:
                 self._check(inst, value)
@@ -124,6 +127,7 @@ def getFields(schema):
             fields[name] = attr
     return fields
 
+
 class _DocStringHelpers(object):
     # Namespace object to hold methods related to ReST formatting
     # docstrings
@@ -286,7 +290,9 @@ class Field(Attribute):
     def validate(self, value):
         if value == self.missing_value:
             if self.required:
-                raise RequiredMissing(self.__name__).with_field_and_value(self, value)
+                raise RequiredMissing(
+                    self.__name__
+                ).with_field_and_value(self, value)
         else:
             try:
                 self._validate(value)
@@ -307,18 +313,21 @@ class Field(Attribute):
     def __hash__(self):
         # Equal objects should have equal hashes;
         # equal hashes does not imply equal objects.
-        value = (type(self), self.interface) + tuple(self.__get_property_names_to_compare())
+        value = (
+            (type(self), self.interface) +
+            tuple(self.__get_property_names_to_compare())
+        )
         return hash(value)
 
     def __eq__(self, other):
-        # should be the same type and in the same interface (or no interface at all)
+        # should be the same type and in the same interface (or no interface
+        # at all)
         if self is other:
             return True
 
         if type(self) != type(other) or self.interface != other.interface:
             return False
 
-
         # should have the same properties
         names = self.__get_property_names_to_compare()
         # XXX: What about the property names of the other object? Even
@@ -335,7 +344,9 @@ class Field(Attribute):
 
     def _validate(self, value):
         if self._type is not None and not isinstance(value, self._type):
-            raise WrongType(value, self._type, self.__name__).with_field_and_value(self, value)
+            raise WrongType(
+                value, self._type, self.__name__
+            ).with_field_and_value(self, value)
 
         try:
             constraint = self.constraint(value)
@@ -346,7 +357,9 @@ class Field(Attribute):
                 e.value = value
             raise
         if not constraint:
-            raise ConstraintNotSatisfied(value, self.__name__).with_field_and_value(self, value)
+            raise ConstraintNotSatisfied(
+                value, self.__name__
+            ).with_field_and_value(self, value)
 
     def get(self, object):
         return getattr(object, self.__name__)
@@ -380,16 +393,20 @@ class Field(Attribute):
         """
 
         lines = []
-        lines.append(_DocStringHelpers.make_class_field('Implementation', type(self)))
+        lines.append(_DocStringHelpers.make_class_field(
+            'Implementation', type(self)))
         lines.append(_DocStringHelpers.make_field("Read Only", self.readonly))
         lines.append(_DocStringHelpers.make_field("Required", self.required))
         if self.defaultFactory:
-            lines.append(_DocStringHelpers.make_field("Default Factory", repr(self.defaultFactory)))
+            lines.append(_DocStringHelpers.make_field(
+                "Default Factory", repr(self.defaultFactory)))
         else:
-            lines.append(_DocStringHelpers.make_field("Default Value", repr(self.default)))
+            lines.append(_DocStringHelpers.make_field(
+                "Default Value", repr(self.default)))
 
         if self._type:
-            lines.append(_DocStringHelpers.make_class_field("Allowed Type", self._type))
+            lines.append(_DocStringHelpers.make_class_field(
+                "Allowed Type", self._type))
 
         # key_type and value_type are commonly used, but don't
         # have a common superclass to add them, so we do it here.
@@ -413,6 +430,7 @@ class Field(Attribute):
 
         return '\n'.join(lines)
 
+
 class Container(Field):
 
     def _validate(self, value):
@@ -495,10 +513,12 @@ class MinMaxLen(object):
         super(MinMaxLen, self)._validate(value)
 
         if self.min_length is not None and len(value) < self.min_length:
-            raise TooShort(value, self.min_length).with_field_and_value(self, value)
+            raise TooShort(value, self.min_length).with_field_and_value(
+                self, value)
 
         if self.max_length is not None and len(value) > self.max_length:
-            raise TooLong(value, self.max_length).with_field_and_value(self, value)
+            raise TooLong(value, self.max_length).with_field_and_value(
+                self, value)
 
 
 @implementer(IFromUnicode)
@@ -514,15 +534,13 @@ class Text(MinMaxLen, Field):
 
     def fromUnicode(self, value):
         """
-        >>> from zope.schema.interfaces import WrongType
-        >>> from zope.schema.interfaces import ConstraintNotSatisfied
         >>> from zope.schema import Text
-        >>> from zope.schema._compat import text_type
         >>> t = Text(constraint=lambda v: 'x' in v)
         >>> t.fromUnicode(b"foo x spam") # doctest: +IGNORE_EXCEPTION_DETAIL
         Traceback (most recent call last):
         ...
-        zope.schema._bootstrapinterfaces.WrongType: ('foo x spam', <type 'unicode'>, '')
+        zope.schema._bootstrapinterfaces.WrongType:
+            ('foo x spam', <type 'unicode'>, '')
         >>> result = t.fromUnicode(u"foo x spam")
         >>> isinstance(result, bytes)
         False
@@ -531,11 +549,13 @@ class Text(MinMaxLen, Field):
         >>> t.fromUnicode(u"foo spam") # doctest: +IGNORE_EXCEPTION_DETAIL
         Traceback (most recent call last):
         ...
-        zope.schema._bootstrapinterfaces.ConstraintNotSatisfied: (u'foo spam', '')
+        zope.schema._bootstrapinterfaces.ConstraintNotSatisfied:
+            (u'foo spam', '')
         """
         if isinstance(value, text_type):
             if self.unicode_normalization:
-                value = unicodedata.normalize(self.unicode_normalization, value)
+                value = unicodedata.normalize(
+                    self.unicode_normalization, value)
         self.validate(value)
         return value
 
@@ -669,7 +689,8 @@ class Number(Orderable, Field):
         (1+0j)
         >>> f.fromUnicode(u"1/2")
         Fraction(1, 2)
-        >>> f.fromUnicode(str(2**31234) + '.' + str(2**256)) # doctest: +ELLIPSIS
+        >>> f.fromUnicode(str(2**31234) + '.' + str(2**256))
+        ... # doctest: +ELLIPSIS
         Decimal('234...936')
         >>> f.fromUnicode(u"not a number") # doctest: +IGNORE_EXCEPTION_DETAIL
         Traceback (most recent call last):
@@ -688,7 +709,8 @@ class Number(Orderable, Field):
         (1+0j)
         >>> f.fromBytes(b"1/2")
         Fraction(1, 2)
-        >>> f.fromBytes((str(2**31234) + '.' + str(2**256)).encode('ascii')) # doctest: +ELLIPSIS
+        >>> f.fromBytes((str(2**31234) + '.' + str(2**256)).encode('ascii'))
+        ... # doctest: +ELLIPSIS
         Decimal('234...936')
         >>> f.fromBytes(b"not a number") # doctest: +IGNORE_EXCEPTION_DETAIL
         Traceback (most recent call last):
@@ -702,14 +724,16 @@ class Number(Orderable, Field):
     """
     _type = numbers.Number
 
-    # An ordered sequence of conversion routines. These should accept
-    # a native string and produce an object that is an instance of `_type`, or raise
-    # a ValueError. The order should be most specific/strictest towards least
-    # restrictive (in other words, lowest in the numeric tower towards highest).
-    # We break this rule with fractions, though: a floating point number is
-    # more generally useful and expected than a fraction, so we attempt to parse
-    # as a float before a fraction.
-    _unicode_converters = (int, float, fractions.Fraction, complex, decimal.Decimal)
+    # An ordered sequence of conversion routines. These should accept a
+    # native string and produce an object that is an instance of `_type`, or
+    # raise a ValueError. The order should be most specific/strictest
+    # towards least restrictive (in other words, lowest in the numeric tower
+    # towards highest). We break this rule with fractions, though: a
+    # floating point number is more generally useful and expected than a
+    # fraction, so we attempt to parse as a float before a fraction.
+    _unicode_converters = (
+        int, float, fractions.Fraction, complex, decimal.Decimal,
+    )
 
     # The type of error we will raise if all conversions fail.
     _validation_error = InvalidNumberLiteral
@@ -719,7 +743,9 @@ class Number(Orderable, Field):
         for converter in self._unicode_converters:
             try:
                 val = converter(value)
-                if converter is float and isinf(val) and decimal.Decimal in self._unicode_converters:
+                if (converter is float
+                        and isinf(val)
+                        and decimal.Decimal in self._unicode_converters):
                     # Pass this on to decimal, if we're allowed
                     val = decimal.Decimal(value)
             except (ValueError, decimal.InvalidOperation) as e:
@@ -728,15 +754,16 @@ class Number(Orderable, Field):
                 self.validate(val)
                 return val
         try:
-            raise self._validation_error(*last_exc.args).with_field_and_value(self, value)
+            raise self._validation_error(*last_exc.args).with_field_and_value(
+                self, value)
         finally:
             last_exc = None
 
     # On Python 2, native strings are byte strings, which is
     # what the converters expect, so we don't need to do any decoding.
-    if PY2: # pragma: no cover
+    if PY2:  # pragma: PY2
         fromBytes = fromUnicode
-    else:
+    else:    # pragma: PY3
         def fromBytes(self, value):
             return self.fromUnicode(value.decode('utf-8'))
 
@@ -759,7 +786,8 @@ class Complex(Number):
         (1+0j)
         >>> f.fromUnicode(u"1/2")
         Fraction(1, 2)
-        >>> f.fromUnicode(str(2**31234) + '.' + str(2**256)) # doctest: +ELLIPSIS
+        >>> f.fromUnicode(str(2**31234) + '.' + str(2**256))
+        ... # doctest: +ELLIPSIS
         inf
         >>> f.fromUnicode(u"not a number") # doctest: +IGNORE_EXCEPTION_DETAIL
         Traceback (most recent call last):
@@ -778,7 +806,8 @@ class Complex(Number):
         (1+0j)
         >>> f.fromBytes(b"1/2")
         Fraction(1, 2)
-        >>> f.fromBytes((str(2**31234) + '.' + str(2**256)).encode('ascii')) # doctest: +ELLIPSIS
+        >>> f.fromBytes((str(2**31234) + '.' + str(2**256)).encode('ascii'))
+        ... # doctest: +ELLIPSIS
         inf
         >>> f.fromBytes(b"not a number") # doctest: +IGNORE_EXCEPTION_DETAIL
         Traceback (most recent call last):
@@ -811,7 +840,8 @@ class Real(Complex):
         InvalidNumberLiteral: Invalid literal for Fraction: '1+0j'
         >>> f.fromUnicode("1/2")
         Fraction(1, 2)
-        >>> f.fromUnicode(str(2**31234) + '.' + str(2**256)) # doctest: +ELLIPSIS
+        >>> f.fromUnicode(str(2**31234) + '.' + str(2**256))
+        ... # doctest: +ELLIPSIS
         inf
         >>> f.fromUnicode("not a number") # doctest: +IGNORE_EXCEPTION_DETAIL
         Traceback (most recent call last):
@@ -844,7 +874,8 @@ class Rational(Real):
         Traceback (most recent call last):
         ...
         InvalidNumberLiteral: Invalid literal for Fraction: '1+0j'
-        >>> f.fromUnicode(str(2**31234) + '.' + str(2**256)) # doctest: +ELLIPSIS
+        >>> f.fromUnicode(str(2**31234) + '.' + str(2**256))
+        ... # doctest: +ELLIPSIS
         Fraction(777..., 330...)
         >>> f.fromUnicode("not a number") # doctest: +IGNORE_EXCEPTION_DETAIL
         Traceback (most recent call last):
@@ -929,7 +960,8 @@ class Decimal(Number):
         Traceback (most recent call last):
         ...
         InvalidDecimalLiteral: Invalid literal for Decimal(): 1/2
-        >>> f.fromUnicode(str(2**31234) + '.' + str(2**256)) # doctest: +ELLIPSIS
+        >>> f.fromUnicode(str(2**31234) + '.' + str(2**256))
+        ... # doctest: +ELLIPSIS
         Decimal('2349...936')
         >>> f.fromUnicode("not a number") # doctest: +IGNORE_EXCEPTION_DETAIL
         Traceback (most recent call last):
@@ -952,7 +984,8 @@ class Decimal(Number):
         Traceback (most recent call last):
         ...
         InvalidDecimalLiteral: Invalid literal for Decimal(): 1/2
-        >>> f.fromBytes((str(2**31234) + '.' + str(2**256)).encode("ascii")) # doctest: +ELLIPSIS
+        >>> f.fromBytes((str(2**31234) + '.' + str(2**256)).encode("ascii"))
+        ... # doctest: +ELLIPSIS
         Decimal('2349...936')
         >>> f.fromBytes(b"not a number") # doctest: +IGNORE_EXCEPTION_DETAIL
         Traceback (most recent call last):
@@ -1010,7 +1043,7 @@ def get_schema_validation_errors(schema, value,
         for name in schema.names(all=True):
             attribute = schema[name]
             if IMethod.providedBy(attribute):
-                continue # pragma: no cover
+                continue  # pragma: no cover
 
             try:
                 if IValidatable.providedBy(attribute):
@@ -1022,7 +1055,9 @@ def get_schema_validation_errors(schema, value,
                 errors[name] = error
             except AttributeError as error:
                 # property for the given name is not implemented
-                errors[name] = SchemaNotFullyImplemented(error).with_field_and_value(attribute, None)
+                errors[name] = SchemaNotFullyImplemented(
+                    error
+                ).with_field_and_value(attribute, None)
     finally:
         ids_being_validated.remove(id_value)
     return errors
@@ -1074,12 +1109,13 @@ class Object(Field):
         """
         Object(schema=<Not Given>, *, validate_invariants=True, **kwargs)
 
-        Create an `~.IObject` field. The keyword arguments are as for `~.Field`.
+        Create an `~.IObject` field. The keyword arguments are as for
+        `~.Field`.
 
         .. versionchanged:: 4.6.0
-           Add the keyword argument *validate_invariants*. When true (the default),
-           the schema's ``validateInvariants`` method will be invoked to check
-           the ``@invariant`` properties of the schema.
+           Add the keyword argument *validate_invariants*. When true (the
+           default), the schema's ``validateInvariants`` method will be
+           invoked to check the ``@invariant`` properties of the schema.
         .. versionchanged:: 4.6.0
            The *schema* argument can be ommitted in a subclass
            that specifies a ``schema`` attribute.
@@ -1099,7 +1135,8 @@ class Object(Field):
 
     def getExtraDocLines(self):
         lines = super(Object, self).getExtraDocLines()
-        lines.append(_DocStringHelpers.make_class_field("Must Provide", self.schema))
+        lines.append(_DocStringHelpers.make_class_field(
+            "Must Provide", self.schema))
         return lines
 
     def _validate(self, value):
@@ -1107,7 +1144,8 @@ class Object(Field):
 
         # schema has to be provided by value
         if not self.schema.providedBy(value):
-            raise SchemaNotProvided(self.schema, value).with_field_and_value(self, value)
+            raise SchemaNotProvided(self.schema, value).with_field_and_value(
+                self, value)
 
         # check the value against schema
         schema_error_dict, invariant_errors = get_validation_errors(
diff --git a/src/zope/schema/_bootstrapinterfaces.py b/src/zope/schema/_bootstrapinterfaces.py
index 79f9c49..8bddae1 100644
--- a/src/zope/schema/_bootstrapinterfaces.py
+++ b/src/zope/schema/_bootstrapinterfaces.py
@@ -24,6 +24,7 @@ from zope.schema._messageid import _
 # pylint:disable=inherit-non-class,keyword-arg-before-vararg,
 # pylint:disable=no-self-argument
 
+
 class StopValidation(Exception):
     """Raised if the validation is completed early.
 
@@ -219,14 +220,17 @@ class SchemaNotCorrectlyImplemented(WrongContainedType):
     #: of the schema.
     invariant_errors = ()
 
-    def __init__(self, errors=None, name=None, schema_errors=None, invariant_errors=(), *args):
+    def __init__(self, errors=None, name=None, schema_errors=None,
+                 invariant_errors=(), *args):
         """
-        SchemaNotCorrectlyImplemented(errors, name, schema_errors, invariant_errors)
+        SchemaNotCorrectlyImplemented(errors, name, schema_errors,
+                                      invariant_errors)
 
         .. versionchanged:: 4.7.0
            Added named arguments to the constructor.
         """
-        super(SchemaNotCorrectlyImplemented, self).__init__(errors, name, *args)
+        super(SchemaNotCorrectlyImplemented, self).__init__(
+            errors, name, *args)
         self.schema_errors = schema_errors
         self.invariant_errors = invariant_errors
 
@@ -344,7 +348,7 @@ class IValidatable(zope.interface.Interface):
 
 
 class NO_VALUE(object):
-    def __repr__(self): # pragma: no cover
+    def __repr__(self):  # pragma: no cover
         return '<NO_VALUE>'
 
 
diff --git a/src/zope/schema/_compat.py b/src/zope/schema/_compat.py
index 239c8d6..51a4716 100644
--- a/src/zope/schema/_compat.py
+++ b/src/zope/schema/_compat.py
@@ -22,15 +22,15 @@ if PY3:  # pragma: no cover
 
 else:  # pragma: no cover
 
-    string_types = basestring,
-    text_type = unicode
-    binary_type = str
-    integer_types = (int, long)
+    string_types = (basestring, )   # noqa: F821
+    text_type = unicode             # noqa: F821
+    binary_type = str               # noqa: F821
+    integer_types = (int, long)     # noqa: F821
 
     def non_native_string(x):
-        if isinstance(x, unicode):
+        if isinstance(x, unicode):  # noqa: F821
             return x
-        return unicode(x, 'unicode_escape')
+        return unicode(x, 'unicode_escape')  # noqa: F821
 
     def make_binary(x):
         if isinstance(x, str):
diff --git a/src/zope/schema/_field.py b/src/zope/schema/_field.py
index aab68ec..3e42f67 100644
--- a/src/zope/schema/_field.py
+++ b/src/zope/schema/_field.py
@@ -17,7 +17,7 @@ __docformat__ = 'restructuredtext'
 
 try:
     from collections import abc
-except ImportError: # pragma: no cover
+except ImportError:  # pragma: PY2
     # Python 2
     import collections as abc
 
@@ -107,7 +107,7 @@ from zope.schema._bootstrapfields import Bool
 from zope.schema._bootstrapfields import Int
 from zope.schema._bootstrapfields import Integral
 from zope.schema._bootstrapfields import Number
-from zope.schema._bootstrapfields import InvalidDecimalLiteral  # reimport
+from zope.schema._bootstrapfields import InvalidDecimalLiteral  # noqa: reexport
 from zope.schema._bootstrapfields import Decimal
 from zope.schema._bootstrapfields import Password
 from zope.schema._bootstrapfields import Rational
@@ -207,8 +207,8 @@ class NativeString(Text if PY3 else Bytes):
     :class:`~zope.schema.interfaces.IFromBytes`.
 
     .. versionchanged:: 4.9.0
-       This is now a distinct type instead of an alias for either `Text` or `Bytes`,
-       depending on the platform.
+       This is now a distinct type instead of an alias for either `Text` or
+       `Bytes`, depending on the platform.
     """
     _type = str
 
@@ -302,7 +302,8 @@ class Float(Real):
         Traceback (most recent call last):
         ...
         InvalidFloatLiteral: invalid literal for float(): 1/2
-        >>> f.fromUnicode(str(2**31234) + '.' + str(2**256)) # doctest: +ELLIPSIS
+        >>> f.fromUnicode(str(2**31234) + '.' + str(2**256))
+        ... # doctest: +ELLIPSIS
         inf
         >>> f.fromUnicode("not a number") # doctest: +IGNORE_EXCEPTION_DETAIL
         Traceback (most recent call last):
@@ -325,7 +326,8 @@ class Float(Real):
         Traceback (most recent call last):
         ...
         InvalidFloatLiteral: invalid literal for float(): 1/2
-        >>> f.fromBytes((str(2**31234) + '.' + str(2**256)).encode('ascii')) # doctest: +ELLIPSIS
+        >>> f.fromBytes((str(2**31234) + '.' + str(2**256)).encode('ascii'))
+        ... # doctest: +ELLIPSIS
         inf
         >>> f.fromBytes(b"not a number") # doctest: +IGNORE_EXCEPTION_DETAIL
         Traceback (most recent call last):
@@ -355,7 +357,9 @@ class Date(Orderable, Field):
     def _validate(self, value):
         super(Date, self)._validate(value)
         if isinstance(value, datetime):
-            raise WrongType(value, self._type, self.__name__).with_field_and_value(self, value)
+            raise WrongType(
+                value, self._type, self.__name__
+            ).with_field_and_value(self, value)
 
 
 @implementer(ITimedelta)
@@ -376,6 +380,7 @@ class MissingVocabularyError(ValidationError,
     """Raised when a named vocabulary cannot be found."""
     # Subclasses ValueError and LookupError for backwards compatibility
 
+
 class InvalidVocabularyError(ValidationError,
                              ValueError,
                              TypeError):
@@ -383,7 +388,8 @@ class InvalidVocabularyError(ValidationError,
     # Subclasses TypeError and ValueError for backwards compatibility
 
     def __init__(self, vocabulary):
-        super(InvalidVocabularyError, self).__init__("Invalid vocabulary %r" % (vocabulary,))
+        super(InvalidVocabularyError, self).__init__(
+            "Invalid vocabulary %r" % (vocabulary,))
 
 
 @implementer(IChoice, IFromUnicode)
@@ -442,7 +448,8 @@ class Choice(Field):
         # an exception if this isn't possible, and returning
         # an ISource otherwise.
         vocabulary = self.vocabulary
-        if IContextSourceBinder.providedBy(vocabulary) and self.context is not None:
+        if (IContextSourceBinder.providedBy(vocabulary)
+                and self.context is not None):
             vocabulary = vocabulary(self.context)
         elif vocabulary is None and self.vocabularyName is not None:
             vr = getVocabularyRegistry()
@@ -450,11 +457,13 @@ class Choice(Field):
                 vocabulary = vr.get(self.context, self.vocabularyName)
             except LookupError:
                 raise MissingVocabularyError(
-                    "Can't validate value without vocabulary named %r" % (self.vocabularyName,)
+                    "Can't validate value without vocabulary named %r" % (
+                        self.vocabularyName,)
                 ).with_field_and_value(self, value)
 
         if not ISource.providedBy(vocabulary):
-            raise InvalidVocabularyError(vocabulary).with_field_and_value(self, value)
+            raise InvalidVocabularyError(vocabulary).with_field_and_value(
+                self, value)
 
         return vocabulary
 
@@ -480,7 +489,9 @@ class Choice(Field):
         super(Choice, self)._validate(value)
         vocabulary = self._resolve_vocabulary(value)
         if value not in vocabulary:
-            raise ConstraintNotSatisfied(value, self.__name__).with_field_and_value(self, value)
+            raise ConstraintNotSatisfied(
+                value, self.__name__
+            ).with_field_and_value(self, value)
 
 
 # Both of these are inherited from the parent; re-declaring them
@@ -498,9 +509,10 @@ class _StrippedNativeStringLine(NativeStringLine):
         # unicode, but we don't want to allow non-ASCII values, to match
         # Python 2 (our regexs would reject that anyway.)
         try:
-            v = v.encode('ascii') # bytes
+            v = v.encode('ascii')  # bytes
         except UnicodeEncodeError:
-            raise self._invalid_exc_type(value).with_field_and_value(self, value)
+            raise self._invalid_exc_type(value).with_field_and_value(
+                self, value)
         if not isinstance(v, self._type):
             v = v.decode('ascii')
         self.validate(v)
@@ -636,9 +648,9 @@ class DottedName(_StrippedNativeStringLine):
                 "too few dots; %d required" % self.min_dots, value
             ).with_field_and_value(self, value)
         if self.max_dots is not None and dots > self.max_dots:
-            raise InvalidDottedName("too many dots; no more than %d allowed" %
-                                    self.max_dots, value).with_field_and_value(self, value)
-
+            raise InvalidDottedName(
+                "too many dots; no more than %d allowed" % self.max_dots, value
+            ).with_field_and_value(self, value)
 
 
 @implementer(IId)
@@ -691,7 +703,6 @@ def _validate_sequence(value_type, value, errors=None):
 
     To validate a sequence of various values:
 
-       >>> from zope.schema._compat import text_type
        >>> errors = _validate_sequence(field, (bytearray(b'foo'), u'bar', 1))
        >>> errors
        [WrongType(bytearray(b'foo'), <...>, ''), WrongType(1, <...>, '')]
@@ -703,8 +714,10 @@ def _validate_sequence(value_type, value, errors=None):
     for a new sequence:
 
        >>> errors = _validate_sequence(field, (2, u'baz'), errors)
-       >>> errors
-       [WrongType(bytearray(b'foo'), <...>, ''), WrongType(1, <...>, ''), WrongType(2, <...>, '')]
+       >>> errors # doctest: +NORMALIZE_WHITESPACE
+       [WrongType(bytearray(b'foo'), <...>, ''),
+        WrongType(1, <...>, ''),
+        WrongType(2, <...>, '')]
 
     """
     if errors is None:
@@ -731,7 +744,8 @@ def _validate_uniqueness(self, value):
 @implementer(ICollection)
 class Collection(MinMaxLen, Iterable):
     """
-    A generic collection implementing :class:`zope.schema.interfaces.ICollection`.
+    A generic collection implementing
+    :class:`zope.schema.interfaces.ICollection`.
 
     Subclasses can define the attribute ``value_type`` to be a field
     such as an :class:`Object` that will be checked for each member of
@@ -754,7 +768,8 @@ class Collection(MinMaxLen, Iterable):
         if value_type is not _NotGiven:
             self.value_type = value_type
 
-        if self.value_type is not None and not IField.providedBy(self.value_type):
+        if (self.value_type is not None
+                and not IField.providedBy(self.value_type)):
             raise ValueError("'value_type' must be field instance.")
         if unique is not _NotGiven:
             self.unique = unique
@@ -773,7 +788,9 @@ class Collection(MinMaxLen, Iterable):
         errors = _validate_sequence(self.value_type, value)
         if errors:
             try:
-                raise WrongContainedType(errors, self.__name__).with_field_and_value(self, value)
+                raise WrongContainedType(
+                    errors, self.__name__
+                ).with_field_and_value(self, value)
             finally:
                 # Break cycles
                 del errors
@@ -825,7 +842,7 @@ class _AbstractSet(Collection):
 
     def __init__(self, *args, **kwargs):
         super(_AbstractSet, self).__init__(*args, **kwargs)
-        if not self.unique: # set members are always unique
+        if not self.unique:  # set members are always unique
             raise TypeError(
                 "__init__() got an unexpected keyword argument 'unique'")
 
@@ -872,7 +889,9 @@ class Mapping(MinMaxLen, Iterable):
 
         if errors:
             try:
-                raise WrongContainedType(errors, self.__name__).with_field_and_value(self, value)
+                raise WrongContainedType(
+                    errors, self.__name__
+                ).with_field_and_value(self, value)
             finally:
                 # Break cycles
                 del errors
diff --git a/src/zope/schema/_schema.py b/src/zope/schema/_schema.py
index b64b7b6..bd9d780 100644
--- a/src/zope/schema/_schema.py
+++ b/src/zope/schema/_schema.py
@@ -70,7 +70,10 @@ def getValidationErrors(schema, value):
         # Valid! Yay!
         return []
 
-    return list(schema_error_dict.items()) + [(None, e) for e in invariant_errors]
+    return (
+        list(schema_error_dict.items()) +
+        [(None, e) for e in invariant_errors]
+    )
 
 
 def getSchemaValidationErrors(schema, value):
diff --git a/src/zope/schema/accessors.py b/src/zope/schema/accessors.py
index decf3aa..257eb7b 100644
--- a/src/zope/schema/accessors.py
+++ b/src/zope/schema/accessors.py
@@ -76,17 +76,18 @@ class FieldReadAccessor(Method):
             if iface in provided_list:
                 provided_list.remove(iface)
         provided = Declaration(*provided_list)
+        # pylint:disable=broad-except
         try:
             return provided + implemented
-        except BaseException as e: # pragma: no cover pylint:disable=broad-except
+        except BaseException as e:  # pragma: no cover
             # Sadly, zope.interface catches and silently ignores
             # any exceptions raised in ``__providedBy__``,
             # which is the class descriptor that invokes ``__provides__``.
             # So, for example, if we're in strict C3 mode and fail to produce
-            # a resolution order, that gets ignored and we fallback to just what's
-            # implemented by the class.
-            # That's not good. Do our best to propagate the exception by returning it.
-            # There will be downstream errors later.
+            # a resolution order, that gets ignored and we fallback to just
+            # what's implemented by the class.
+            # That's not good. Do our best to propagate the exception by
+            # returning it. There will be downstream errors later.
             return e
 
     def getSignatureString(self):
diff --git a/src/zope/schema/interfaces.py b/src/zope/schema/interfaces.py
index 303380a..c18e54c 100644
--- a/src/zope/schema/interfaces.py
+++ b/src/zope/schema/interfaces.py
@@ -463,7 +463,8 @@ class INativeStringLine(ITextLine if PY3 else IBytesLine):
 
 
 class IPassword(ITextLine):
-    "Field containing a unicode string without newlines that is a password."
+    """Field containing a unicode password string without newlines."""
+
 
 ###
 # Numbers
@@ -550,6 +551,7 @@ class IReal(IComplex):
                         field value""")
         )
 
+
 class IRational(IReal):
     """
     Field containing a rational number: :class:`numbers.IRational`.
@@ -576,6 +578,7 @@ class IRational(IReal):
                         field value""")
         )
 
+
 class IIntegral(IRational):
     """
     Field containing an integral number: class:`numbers.Integral`.
@@ -600,6 +603,8 @@ class IIntegral(IRational):
         description=_("""The field default value may be None or a legal
                         field value""")
         )
+
+
 ##
 # Concrete numbers
 ##
@@ -667,6 +672,7 @@ class IDecimal(INumber):
 # End numbers
 ###
 
+
 class IDatetime(IMinMax, IField):
     """Field containing a datetime."""
 
@@ -757,6 +763,7 @@ class IChoice(IField):
         default=None
         )
 
+
 # Collections:
 
 # Abstract
@@ -792,6 +799,7 @@ class IMutableSequence(ISequence):
     .. versionadded:: 4.6.0
     """
 
+
 class IUnorderedCollection(ICollection):
     """Abstract interface specifying that the value cannot be ordered"""
 
@@ -799,14 +807,16 @@ class IUnorderedCollection(ICollection):
 class IAbstractSet(IUnorderedCollection):
     """An unordered collection of unique values."""
 
-    unique = Bool(description="This ICollection interface attribute must be True")
+    unique = Bool(
+        description="This ICollection interface attribute must be True")
 
 
 class IAbstractBag(IUnorderedCollection):
     """An unordered collection of values, with no limitations on whether
     members are unique"""
 
-    unique = Bool(description="This ICollection interface attribute must be False")
+    unique = Bool(
+        description="This ICollection interface attribute must be False")
 
 
 # Concrete
@@ -844,18 +854,19 @@ class IObject(IField):
 
     schema = Object(
         IInterface,
-        description=_("The Interface that defines the Fields comprising the Object.")
+        description=_("The Interface that defines the Fields comprising the "
+                      "Object.")
     )
 
     validate_invariants = Bool(
         title=_("Validate Invariants"),
-        description=_("A boolean that says whether ``schema.validateInvariants`` "
-                      "is called from ``self.validate()``. The default is true."),
+        description=_("A boolean that says whether "
+                      "``schema.validateInvariants`` is called from "
+                      "``self.validate()``. The default is true."),
         default=True,
     )
 
 
-
 class IMapping(IMinMaxLen, IIterable, IContainer):
     """
     Field containing an instance of :class:`collections.Mapping`.
@@ -866,7 +877,8 @@ class IMapping(IMinMaxLen, IIterable, IContainer):
     """
     key_type = Object(
         IField,
-        description=_("Field keys must conform to the given type, expressed via a Field.")
+        description=_("Field keys must conform to the given type, expressed "
+                      "via a Field.")
     )
 
     value_type = Object(
diff --git a/src/zope/schema/tests/__init__.py b/src/zope/schema/tests/__init__.py
index b7d1a56..f6718f0 100644
--- a/src/zope/schema/tests/__init__.py
+++ b/src/zope/schema/tests/__init__.py
@@ -6,44 +6,46 @@ import re
 from zope.schema._compat import PY3
 from zope.testing import renormalizing
 
-if PY3:
-    py3_checker = renormalizing.RENormalizing([
-        (re.compile(r"u'([^']*)'"),
-                    r"'\1'"),
-        (re.compile(r"^b'([^']*)'"),
-                    r"'\1'"),
-        (re.compile(r"([^'])b'([^']*)'"),
-                    r"\1'\2'"),
-        (re.compile(r"<class 'bytes'>"),
-                    r"<type 'str'>"),
-        (re.compile(r"<class 'str'>"),
-                    r"<type 'unicode'>"),
-        (re.compile(r"zope.schema._bootstrapinterfaces.InvalidValue"),
-                    r"InvalidValue"),
-        (re.compile(r"zope.schema.interfaces.InvalidId: '([^']*)'"),
-                    r"InvalidId: \1"),
-        (re.compile(r"zope.schema.interfaces.InvalidId:"),
-                    r"InvalidId:"),
-        (re.compile(r"zope.schema.interfaces.InvalidURI: '([^']*)'"),
-                    r"InvalidURI: \1"),
-        (re.compile(r"zope.schema.interfaces.InvalidURI:"),
-                    r"InvalidURI:"),
-        (re.compile(r"zope.schema.interfaces.InvalidDottedName: '([^']*)'"),
-                    r"InvalidDottedName: \1"),
-        (re.compile(r"zope.schema.interfaces.InvalidDottedName:"),
-                    r"InvalidDottedName:"),
-        (re.compile(
-          r"zope.schema._bootstrapinterfaces.ConstraintNotSatisfied: '([^']*)'"
-                   ),
-                    r"ConstraintNotSatisfied: \1"),
-        (re.compile(
-           r"zope.schema._bootstrapinterfaces.ConstraintNotSatisfied:"),
-                    r"ConstraintNotSatisfied:"),
-        (re.compile(r"zope.schema._bootstrapinterfaces.WrongType:"),
-                    r"WrongType:"),
-      ])
-else: # pragma: no cover
-    py3_checker = renormalizing.RENormalizing([
-        (re.compile(r"([^'])b'([^']*)'"),
-                    r"\1'\2'"),
-        ])
+
+def _make_transforms(patterns):
+    return [(re.compile(pattern), repl) for pattern, repl in patterns]
+
+
+if PY3:  # pragma: PY3
+    py3_checker = renormalizing.RENormalizing(_make_transforms([
+        (r"u'([^']*)'",
+         r"'\1'"),
+        (r"^b'([^']*)'",
+         r"'\1'"),
+        (r"([^'])b'([^']*)'",
+         r"\1'\2'"),
+        (r"<class 'bytes'>",
+         r"<type 'str'>"),
+        (r"<class 'str'>",
+         r"<type 'unicode'>"),
+        (r"zope.schema._bootstrapinterfaces.InvalidValue",
+         r"InvalidValue"),
+        (r"zope.schema.interfaces.InvalidId: '([^']*)'",
+         r"InvalidId: \1"),
+        (r"zope.schema.interfaces.InvalidId:",
+         r"InvalidId:"),
+        (r"zope.schema.interfaces.InvalidURI: '([^']*)'",
+         r"InvalidURI: \1"),
+        (r"zope.schema.interfaces.InvalidURI:",
+         r"InvalidURI:"),
+        (r"zope.schema.interfaces.InvalidDottedName: '([^']*)'",
+         r"InvalidDottedName: \1"),
+        (r"zope.schema.interfaces.InvalidDottedName:",
+         r"InvalidDottedName:"),
+        (r"zope.schema._bootstrapinterfaces.ConstraintNotSatisfied: '([^']*)'",
+         r"ConstraintNotSatisfied: \1"),
+        (r"zope.schema._bootstrapinterfaces.ConstraintNotSatisfied:",
+         r"ConstraintNotSatisfied:"),
+        (r"zope.schema._bootstrapinterfaces.WrongType:",
+         r"WrongType:"),
+    ]))
+else:  # pragma: PY2
+    py3_checker = renormalizing.RENormalizing(_make_transforms([
+        (r"([^'])b'([^']*)'",
+         r"\1'\2'"),
+    ]))
diff --git a/src/zope/schema/tests/states.py b/src/zope/schema/tests/states.py
index 3507fb2..dc3ca70 100644
--- a/src/zope/schema/tests/states.py
+++ b/src/zope/schema/tests/states.py
@@ -16,7 +16,6 @@
 
 from zope.interface import implementer
 from zope.schema import interfaces
-from zope.schema import Choice
 
 # This table is based on information from the United States Postal Service:
 # http://www.usps.com/ncsc/lookups/abbreviations.html#states
@@ -91,6 +90,7 @@ class State(object):
         self.value = value
         self.title = title
 
+
 for v, p in _states.items():
     _states[v] = State(v, p)
 
diff --git a/src/zope/schema/tests/test__bootstrapfields.py b/src/zope/schema/tests/test__bootstrapfields.py
index 58e7e31..3516bf6 100644
--- a/src/zope/schema/tests/test__bootstrapfields.py
+++ b/src/zope/schema/tests/test__bootstrapfields.py
@@ -19,6 +19,7 @@ import unicodedata
 # pylint:disable=protected-access,inherit-non-class,blacklisted-name
 # pylint:disable=attribute-defined-outside-init
 
+
 class InterfaceConformanceTestsMixin(object):
 
     def _getTargetClass(self):
@@ -66,13 +67,15 @@ class InterfaceConformanceTestsMixin(object):
         from zope.interface import ro
         from zope.interface import implementedBy
         __traceback_info__ = implementedBy(self._getTargetClass()).__sro__
-        self.assertTrue(ro.is_consistent(implementedBy(self._getTargetClass())))
+        self.assertTrue(
+            ro.is_consistent(implementedBy(self._getTargetClass())))
 
     def test_iface_consistent_ro(self):
         from zope.interface import ro
         __traceback_info__ = self._getTargetInterface().__iro__
         self.assertTrue(ro.is_consistent(self._getTargetInterface()))
 
+
 class EqualityTestsMixin(InterfaceConformanceTestsMixin):
 
     def test_is_hashable(self):
@@ -244,7 +247,8 @@ class LenTestsMixin(object):
 
 class WrongTypeTestsMixin(object):
 
-    def assertRaisesWrongType(self, field_or_meth, expected_type, *args, **kwargs):
+    def assertRaisesWrongType(self, field_or_meth, expected_type,
+                              *args, **kwargs):
         from zope.schema.interfaces import WrongType
         field = None
         with self.assertRaises(WrongType) as exc:
@@ -265,7 +269,6 @@ class WrongTypeTestsMixin(object):
             # A single keyword argument
             self.assertIs(ex.value, kwargs.popitem()[1])
 
-
     def assertAllRaiseWrongType(self, field, expected_type, *values):
         for value in values:
             __traceback_info__ = value
@@ -986,7 +989,8 @@ class TextTests(EqualityTestsMixin,
         self.assertEqual(txt.fromUnicode(deadbeef), deadbeef)
 
     def test_normalization(self):
-        deadbeef = unicodedata.normalize('NFD', b'\xc3\x84\xc3\x96\xc3\x9c'.decode('utf-8'))
+        deadbeef = unicodedata.normalize(
+            'NFD', b'\xc3\x84\xc3\x96\xc3\x9c'.decode('utf-8'))
         txt = self._makeOne()
         self.assertEqual(txt.unicode_normalization, 'NFC')
         self.assertEqual(
@@ -1016,6 +1020,7 @@ class TextTests(EqualityTestsMixin,
         # see https://github.com/zopefoundation/zope.schema/issues/90
         import pickle
         orig_makeOne = self._makeOne
+
         def makeOne(**kwargs):
             result = orig_makeOne(**kwargs)
             if not kwargs:
@@ -1209,7 +1214,8 @@ class NumberTests(EqualityTestsMixin,
     def test_instance_conforms_to_iface(self):
         from zope.schema._bootstrapinterfaces import IFromUnicode
         from zope.schema._bootstrapinterfaces import IFromBytes
-        verifyObject = super(NumberTests, self).test_instance_conforms_to_iface()
+        verifyObject = (
+            super(NumberTests, self).test_instance_conforms_to_iface())
         verifyObject(IFromUnicode, self._makeOne())
         verifyObject(IFromBytes, self._makeOne())
 
@@ -1224,6 +1230,7 @@ class ComplexTests(NumberTests):
         from zope.schema.interfaces import IComplex
         return IComplex
 
+
 class RealTests(WrongTypeTestsMixin,
                 NumberTests):
 
@@ -1238,8 +1245,10 @@ class RealTests(WrongTypeTestsMixin,
     def test_ctor_real_min_max(self):
         from fractions import Fraction
 
-        self.assertRaisesWrongType(self._makeOne, self._getTargetClass()._type, min='')
-        self.assertRaisesWrongType(self._makeOne, self._getTargetClass()._type, max='')
+        self.assertRaisesWrongType(
+            self._makeOne, self._getTargetClass()._type, min='')
+        self.assertRaisesWrongType(
+            self._makeOne, self._getTargetClass()._type, max='')
 
         field = self._makeOne(min=Fraction(1, 2), max=2)
         field.validate(1.0)
@@ -1394,7 +1403,8 @@ class ObjectTests(EqualityTestsMixin,
     def _makeOneFromClass(self, cls, schema=None, *args, **kw):
         if schema is None:
             schema = self._makeSchema()
-        return super(ObjectTests, self)._makeOneFromClass(cls, schema, *args, **kw)
+        return super(ObjectTests, self)._makeOneFromClass(
+            cls, schema, *args, **kw)
 
     def _makeSchema(self, **kw):
         from zope.interface import Interface
@@ -1749,13 +1759,12 @@ class ObjectTests(EqualityTestsMixin,
                     raise Invalid("Bar is not valid")
 
         @implementer(ISchema)
-        class O(object):
+        class Obj(object):
             foo = u''
             bar = b''
 
-
         field = self._makeOne(ISchema)
-        inst = O()
+        inst = Obj()
 
         # Fine at first
         field.validate(inst)
@@ -1807,7 +1816,6 @@ class ObjectTests(EqualityTestsMixin,
         class ValueType(object):
             "The value type"
 
-
         field.validate(ValueType())
 
     def test_bound_field_of_collection_with_choice(self):
@@ -1823,7 +1831,6 @@ class ObjectTests(EqualityTestsMixin,
         from zope.schema.interfaces import SchemaNotCorrectlyImplemented
         from zope.schema.vocabulary import SimpleVocabulary
 
-
         @implementer(IContextSourceBinder)
         class EnumContext(object):
             def __call__(self, context):
@@ -1832,7 +1839,8 @@ class ObjectTests(EqualityTestsMixin,
         class IMultipleChoice(Interface):
             choices = Set(value_type=Choice(source=EnumContext()))
             # Provide a regular attribute to prove that binding doesn't
-            # choke. NOTE: We don't actually verify the existence of this attribute.
+            # choke. NOTE: We don't actually verify the existence of this
+            # attribute.
             non_field = Attribute("An attribute")
 
         @implementer(IMultipleChoice)
@@ -1843,14 +1851,13 @@ class ObjectTests(EqualityTestsMixin,
 
             def __iter__(self):
                 # EnumContext calls this to make the vocabulary.
-                # Fields of the schema of the IObject are bound to the value being
-                # validated.
+                # Fields of the schema of the IObject are bound to the value
+                # being validated.
                 return iter(range(5))
 
         class IFavorites(Interface):
             fav = Object(title=u"Favorites number", schema=IMultipleChoice)
 
-
         @implementer(IFavorites)
         class Favorites(object):
             fav = FieldProperty(IFavorites['fav'])
@@ -1924,6 +1931,6 @@ def test_suite():
     suite = unittest.defaultTestLoader.loadTestsFromName(__name__)
     suite.addTests(doctest.DocTestSuite(
         zope.schema._bootstrapfields,
-        optionflags=doctest.ELLIPSIS|IGNORE_EXCEPTION_MODULE_IN_PYTHON2
+        optionflags=doctest.ELLIPSIS | IGNORE_EXCEPTION_MODULE_IN_PYTHON2
     ))
     return suite
diff --git a/src/zope/schema/tests/test__bootstrapinterfaces.py b/src/zope/schema/tests/test__bootstrapinterfaces.py
index 77815c0..385fa1c 100644
--- a/src/zope/schema/tests/test__bootstrapinterfaces.py
+++ b/src/zope/schema/tests/test__bootstrapinterfaces.py
@@ -19,6 +19,7 @@ except NameError:
     def compare(a, b):
         return -1 if a < b else (0 if a == b else 1)
 
+
 class ValidationErrorTests(unittest.TestCase):
 
     def _getTargetClass(self):
diff --git a/src/zope/schema/tests/test__field.py b/src/zope/schema/tests/test__field.py
index 13600d5..efbf152 100644
--- a/src/zope/schema/tests/test__field.py
+++ b/src/zope/schema/tests/test__field.py
@@ -29,6 +29,7 @@ from zope.schema.tests.test__bootstrapfields import NumberTests
 # pylint:disable=no-member
 # pylint:disable=blacklisted-name
 
+
 class BytesTests(EqualityTestsMixin,
                  WrongTypeTestsMixin,
                  unittest.TestCase):
@@ -274,7 +275,6 @@ class FloatTests(NumberTests):
     TOO_SMALL = tuple(float(x) for x in NumberTests.TOO_SMALL)
     TOO_BIG = tuple(float(x) for x in NumberTests.TOO_BIG)
 
-
     def _getTargetClass(self):
         from zope.schema._field import Float
         return Float
@@ -448,7 +448,8 @@ class TimedeltaTests(OrderableMissingValueMixin,
     MIN = datetime.timedelta(minutes=NumberTests.MIN)
     MAX = datetime.timedelta(minutes=NumberTests.MAX)
     VALID = tuple(datetime.timedelta(minutes=x) for x in NumberTests.VALID)
-    TOO_SMALL = tuple(datetime.timedelta(minutes=x) for x in NumberTests.TOO_SMALL)
+    TOO_SMALL = tuple(
+        datetime.timedelta(minutes=x) for x in NumberTests.TOO_SMALL)
     TOO_BIG = tuple(datetime.timedelta(x) for x in NumberTests.TOO_BIG)
 
 
@@ -505,9 +506,9 @@ class ChoiceTests(EqualityTestsMixin,
 
     def _makeOneFromClass(self, cls, *args, **kwargs):
         if (not args
-            and 'vocabulary' not in kwargs
-            and 'values' not in kwargs
-            and 'source' not in kwargs):
+                and 'vocabulary' not in kwargs
+                and 'values' not in kwargs
+                and 'source' not in kwargs):
             from zope.schema.vocabulary import SimpleVocabulary
             kwargs['vocabulary'] = SimpleVocabulary.fromValues([1, 2, 3])
         return super(ChoiceTests, self)._makeOneFromClass(cls, *args, **kwargs)
@@ -516,12 +517,12 @@ class ChoiceTests(EqualityTestsMixin,
         from zope.schema.interfaces import IChoice
         return IChoice
 
-
     def test_ctor_wo_values_vocabulary_or_source(self):
         self.assertRaises(ValueError, self._getTargetClass())
 
     def test_ctor_invalid_vocabulary(self):
-        self.assertRaises(ValueError, self._getTargetClass(), vocabulary=object())
+        self.assertRaises(ValueError,
+                          self._getTargetClass(), vocabulary=object())
 
     def test_ctor_invalid_source(self):
         self.assertRaises(ValueError, self._getTargetClass(), source=object())
@@ -552,8 +553,8 @@ class ChoiceTests(EqualityTestsMixin,
                          sorted(values))
         self.assertEqual(
             sorted(choose.vocabulary.by_token.keys()),
-            sorted([x.encode('ascii', 'backslashreplace').decode('ascii') for x in values]))
-
+            sorted([x.encode('ascii', 'backslashreplace').decode('ascii')
+                    for x in values]))
 
     def test_ctor_w_named_vocabulary(self):
         choose = self._makeOne(vocabulary="vocab")
@@ -724,6 +725,7 @@ class ChoiceTests(EqualityTestsMixin,
 
         class Reg(object):
             called_with = ()
+
             def get(self, *args):
                 self.called_with += args
                 return _makeSampleVocabulary()
@@ -1006,7 +1008,8 @@ class DottedNameTests(EqualityTestsMixin,
 
         # Underscores are allowed in any component
         self.assertEqual(field.fromUnicode(u'dotted._name'), 'dotted._name')
-        self.assertEqual(field.fromUnicode(u'_leading_underscore'), '_leading_underscore')
+        self.assertEqual(field.fromUnicode(u'_leading_underscore'),
+                         '_leading_underscore')
         self.assertEqual(field.fromUnicode(u'_dotted.name'), '_dotted.name')
         self.assertEqual(field.fromUnicode(u'_dotted._name'), '_dotted._name')
 
@@ -1181,7 +1184,6 @@ class CollectionTests(EqualityTestsMixin,
 
     _makeCollection = list
 
-
     def test_schema_defined_by_subclass(self):
         from zope import interface
         from zope.schema import Object
@@ -1217,7 +1219,6 @@ class CollectionTests(EqualityTestsMixin,
         class ValueType(object):
             "The value type"
 
-
         field.validate(self._makeCollection([ValueType()]))
 
     def test_ctor_defaults(self):
@@ -1358,6 +1359,7 @@ class SequenceTests(WrongTypeTestsMixin,
         class Sequence(abc.Sequence):
             def __getitem__(self, i):
                 raise AssertionError("Not implemented")
+
             def __len__(self):
                 return 0
 
@@ -1371,16 +1373,20 @@ class SequenceTests(WrongTypeTestsMixin,
         class MutableSequence(abc.MutableSequence):
             def insert(self, index, value):
                 raise AssertionError("not implemented")
+
             def __getitem__(self, name):
                 raise AssertionError("not implemented")
+
             def __iter__(self):
                 return iter(())
+
             def __setitem__(self, name, value):
                 raise AssertionError("Not implemented")
+
             def __len__(self):
                 return 0
-            __delitem__ = __getitem__
 
+            __delitem__ = __getitem__
 
         sequence = MutableSequence()
         field = self._makeOne()
@@ -1479,7 +1485,7 @@ class SetTests(WrongTypeTestsMixin,
 
     def test_ctor_disallows_unique(self):
         self.assertRaises(TypeError, self._makeOne, unique=False)
-        self._makeOne(unique=True) # restating the obvious is allowed
+        self._makeOne(unique=True)  # restating the obvious is allowed
         self.assertTrue(self._makeOne().unique)
 
     def test_validate_wrong_types(self):
@@ -1599,7 +1605,6 @@ class MappingTests(EqualityTestsMixin,
         self.assertIsInstance(wct.errors[0], WrongType)
         self.assertIs(field.value_type._type, wct.errors[0].expected_type)
 
-
     def test_validate_min_length(self):
         field = self._makeOne(min_length=1)
         field.validate({1: 'a'})
@@ -1635,12 +1640,13 @@ class MappingTests(EqualityTestsMixin,
 
             def __getitem__(self, name):
                 raise AssertionError("not implemented")
+
             def __iter__(self):
                 return iter(())
+
             def __len__(self):
                 return 0
 
-
         mm = Mapping()
         field = self._makeOne()
         field.validate(mm)
@@ -1652,12 +1658,16 @@ class MappingTests(EqualityTestsMixin,
 
             def __getitem__(self, name):
                 raise AssertionError("not implemented")
+
             def __iter__(self):
                 return iter(())
+
             def __setitem__(self, name, value):
                 raise AssertionError("Not implemented")
+
             def __len__(self):
                 return 0
+
             __delitem__ = __getitem__
 
         mm = MutableMapping()
@@ -1696,6 +1706,7 @@ class DictTests(MutableMappingTests):
         with self.assertRaises(WrongType):
             super(DictTests, self).test_mutable_mapping()
 
+
 class NativeStringTests(EqualityTestsMixin,
                         WrongTypeTestsMixin,
                         unittest.TestCase):
@@ -1766,7 +1777,8 @@ class StrippedNativeStringLineTests(NativeStringLineTests):
         self.assertEqual(field.fromUnicode(u' '), '')
 
     def test_iface_is_first_in_sro(self):
-        self.skipTest("Not applicable; we inherit implementation but have no interface")
+        self.skipTest("Not applicable; we inherit implementation but have no "
+                      "interface")
 
 
 def _makeSampleVocabulary():
@@ -1782,7 +1794,7 @@ def _makeSampleVocabulary():
         def __contains__(self, value):
             return 0 <= value < 10
 
-        def __len__(self): # pragma: no cover
+        def __len__(self):  # pragma: no cover
             return 10
 
         def getTerm(self, value):
diff --git a/src/zope/schema/tests/test_accessors.py b/src/zope/schema/tests/test_accessors.py
index 2a6ceae..74bd0a2 100644
--- a/src/zope/schema/tests/test_accessors.py
+++ b/src/zope/schema/tests/test_accessors.py
@@ -17,6 +17,7 @@ import unittest
 
 # pylint:disable=inherit-non-class
 
+
 class FieldReadAccessorTests(unittest.TestCase):
 
     def _getTargetClass(self):
@@ -207,7 +208,9 @@ class FieldReadAccessorTests(unittest.TestCase):
             pass
 
         writer = Writer()
-        writer.__name__ = 'setMe' # pylint:disable=attribute-defined-outside-init
+        # pylint:disable=attribute-defined-outside-init
+        writer.__name__ = 'setMe'
+        # pylint:enable=attribute-defined-outside-init
         getter.writer = writer
 
         class Foo(object):
diff --git a/src/zope/schema/tests/test_fieldproperty.py b/src/zope/schema/tests/test_fieldproperty.py
index f319f55..fd2dd5a 100644
--- a/src/zope/schema/tests/test_fieldproperty.py
+++ b/src/zope/schema/tests/test_fieldproperty.py
@@ -288,7 +288,8 @@ class FieldPropertyTests(_Base, _Integration):
         self.assertEqual(event.new_value, 0)
         self.assertEqual(
             [ev.field.__name__ for ev in log],
-            ['min_length', 'max_length', 'title', 'description', 'required', 'readonly'])
+            ['min_length', 'max_length', 'title', 'description', 'required',
+             'readonly'])
 
     def test_field_event_update(self):
         from zope.schema import Text
@@ -517,7 +518,7 @@ class FieldPropertyStoredThroughFieldTests(_Base, _Integration):
                 return default
 
             def set(self, inst, value):
-                if self.readonly: # pragma: no cover
+                if self.readonly:  # pragma: no cover
                     raise ValueError
                 setattr(inst, 'faux', value)
 
@@ -608,7 +609,8 @@ class FieldPropertyStoredThroughFieldTests(_Base, _Integration):
         # these are fieldproperties in the field
         self.assertEqual(
             [ev.field.__name__ for ev in log],
-            ['min_length', 'max_length', 'title', 'description', 'required', 'readonly'])
+            ['min_length', 'max_length', 'title', 'description', 'required',
+             'readonly'])
         event = log[0]
         self.assertTrue(isinstance(event, FieldUpdatedEvent))
         self.assertEqual(event.inst, field)
@@ -622,8 +624,6 @@ def _getSchema():
     from zope.schema import Float
     from zope.schema import Text
 
-
-
     class Schema(Interface):
         title = Text(description=u"Short summary",
                      default=u'say something')
diff --git a/src/zope/schema/tests/test_schema.py b/src/zope/schema/tests/test_schema.py
index f64b5fe..d91452d 100644
--- a/src/zope/schema/tests/test_schema.py
+++ b/src/zope/schema/tests/test_schema.py
@@ -42,8 +42,8 @@ def _makeSchema():
 
 def _makeDerivedSchema(base=None):
 
-
     from zope.schema import Bytes
+
     if base is None:
         base = _makeSchema()
 
@@ -225,7 +225,6 @@ class Test_getSchemaValidationErrors(unittest.TestCase):
         from zope.interface import Interface
         from zope.schema import Text
 
-
         class IWithFields(Interface):
             foo = Text()
             bar = Text()
diff --git a/src/zope/schema/tests/test_vocabulary.py b/src/zope/schema/tests/test_vocabulary.py
index 8dc17ea..eef246b 100644
--- a/src/zope/schema/tests/test_vocabulary.py
+++ b/src/zope/schema/tests/test_vocabulary.py
@@ -72,10 +72,7 @@ class SimpleTermTests(unittest.TestCase):
         self.assertEqual(term.token, 'Snowman \\u2603')
         self.assertFalse(ITitledTokenizedTerm.providedBy(term))
 
-
     def test__eq__and__hash__(self):
-        from zope import interface
-
         term = self._makeOne('value')
         # Equal to itself
         self.assertEqual(term, term)
@@ -387,10 +384,10 @@ class TreeVocabularyTests(unittest.TestCase):
         self.assertTrue(IStupid.providedBy(v))
 
     def test_ordering(self):
-        #The TreeVocabulary makes use of an OrderedDict to store it's
-        #internal tree representation.
+        # The TreeVocabulary makes use of an OrderedDict to store its
+        # internal tree representation.
         #
-        #Check that they keys are indeed oredered.
+        # Check that the keys are indeed ordered.
         from collections import OrderedDict
 
         d = {
@@ -648,7 +645,7 @@ class TreeVocabularyTests(unittest.TestCase):
             self.assertEqual(str(e), "Term tokens must be unique: 'one'")
 
     def test_recursive_methods(self):
-        #Test the _createTermTree and _getPathToTreeNode methods
+        # Test the _createTermTree and _getPathToTreeNode methods
         from zope.schema.vocabulary import _createTermTree
         tree = _createTermTree({}, self.business_tree())
         vocab = self._getTargetClass().fromDict(self.business_tree())
@@ -681,7 +678,7 @@ class TreeVocabularyTests(unittest.TestCase):
 
 
 class RegistryTests(unittest.TestCase):
-    #Tests of the simple vocabulary and presentation registries.
+    # Tests of the simple vocabulary and presentation registries.
 
     def setUp(self):
         from zope.schema.vocabulary import _clear
@@ -723,7 +720,7 @@ def _makeSampleVocabulary():
         def __contains__(self, value):
             return 0 <= value < 10
 
-        def __len__(self): # pragma: no cover
+        def __len__(self):  # pragma: no cover
             return 10
 
         def getTerm(self, value):
diff --git a/src/zope/schema/vocabulary.py b/src/zope/schema/vocabulary.py
index eba0d4b..bab9a67 100644
--- a/src/zope/schema/vocabulary.py
+++ b/src/zope/schema/vocabulary.py
@@ -217,7 +217,10 @@ class SimpleVocabulary(object):
         if not isinstance(other, SimpleVocabulary):
             return False
 
-        return self._terms == other._terms and providedBy(self) == providedBy(other)
+        return (
+            self._terms == other._terms
+            and providedBy(self) == providedBy(other)
+        )
 
     def __ne__(self, other):
         return not self.__eq__(other)
@@ -329,7 +332,8 @@ class TreeVocabulary(object):
 
         The tuples should have either 2 or 3 values, i.e:
         (token, value, title) or (token, value). Only tuples that have
-        three values will create a :class:`zope.schema.interfaces.ITitledTokenizedTerm`.
+        three values will create a
+        :class:`zope.schema.interfaces.ITitledTokenizedTerm`.
 
         For example, a dict with 2-valued tuples::
 
@@ -473,6 +477,7 @@ class VocabularyRegistry(object):
         """Register a *factory* for the vocabulary with the given *name*."""
         self._map[name] = factory
 
+
 _vocabularies = None
 
 
diff --git a/tox.ini b/tox.ini
index feb5397..15641ac 100644
--- a/tox.ini
+++ b/tox.ini
@@ -3,7 +3,7 @@ envlist =
 # Jython support pending 2.7 support, due 2012-07-15 or so.  See:
 # http://fwierzbicki.blogspot.com/2012/03/adconion-to-fund-jython-27.html
 #   py27,jython,pypy,coverage
-    py27,py35,py36,py37,py38,pypy,pypy3,coverage,docs
+    lint,py27,py35,py36,py37,py38,pypy,pypy3,coverage,docs
 
 [testenv]
 deps =
@@ -12,6 +12,16 @@ commands =
     zope-testrunner --test-path=src
     sphinx-build -b doctest -d {envdir}/.cache/doctrees docs {envdir}/.cache/doctest
 
+[testenv:lint]
+usedevelop = true
+basepython =
+    python3.6
+skip_install = true
+deps =
+    flake8
+commands =
+    flake8 src setup.py
+
 [testenv:coverage]
 usedevelop = true
 basepython =
@@ -22,6 +32,7 @@ commands =
 deps =
     .[test]
     coverage
+    coverage-python-version
 
 [testenv:docs]
 basepython =