19 files changed, 121 insertions, 88 deletions

diff --git a/src/flake8/_compat.py b/src/flake8/_compat.py
index 85af0a3..640f2bd 100644
--- a/src/flake8/_compat.py
+++ b/src/flake8/_compat.py
@@ -1,10 +1,6 @@
 """Expose backports in a single place."""
 import sys
-
-if sys.version_info >= (3,):  # pragma: no cover (PY3+)
-    from functools import lru_cache
-else:  # pragma: no cover (<PY3)
-    from functools32 import lru_cache
+from functools import lru_cache
 
 if sys.version_info >= (3, 8):  # pragma: no cover (PY38+)
     import importlib.metadata as importlib_metadata
diff --git a/src/flake8/api/legacy.py b/src/flake8/api/legacy.py
index 7923698..f046b5c 100644
--- a/src/flake8/api/legacy.py
+++ b/src/flake8/api/legacy.py
@@ -60,7 +60,7 @@ def get_style_guide(**kwargs):
     return StyleGuide(application)
 
 
-class StyleGuide(object):
+class StyleGuide:
     """Public facing object that mimic's Flake8 2.0's StyleGuide.
 
     .. note::
@@ -170,7 +170,7 @@ class StyleGuide(object):
         return self.check_files([filename])
 
 
-class Report(object):
+class Report:
     """Public facing object that mimic's Flake8 2.0's API.
 
     .. note::
@@ -210,6 +210,6 @@ class Report(object):
             list
         """
         return [
-            "{} {} {}".format(s.count, s.error_code, s.message)
+            f"{s.count} {s.error_code} {s.message}"
             for s in self._stats.statistics_for(violation)
         ]
diff --git a/src/flake8/checker.py b/src/flake8/checker.py
index 82ce090..a9abd21 100644
--- a/src/flake8/checker.py
+++ b/src/flake8/checker.py
@@ -6,18 +6,21 @@ import logging
 import signal
 import sys
 import tokenize
-from typing import Dict, List, Optional, Tuple
-
-try:
-    import multiprocessing.pool
-except ImportError:
-    multiprocessing = None  # type: ignore
+from typing import Dict
+from typing import List
+from typing import Optional
+from typing import Tuple
 
 from flake8 import defaults
 from flake8 import exceptions
 from flake8 import processor
 from flake8 import utils
 
+try:
+    import multiprocessing.pool
+except ImportError:
+    multiprocessing = None  # type: ignore
+
 LOG = logging.getLogger(__name__)
 
 SERIAL_RETRY_ERRNOS = {
@@ -48,7 +51,7 @@ def _multiprocessing_is_fork():  # type () -> bool
         return multiprocessing and not utils.is_windows()
 
 
-class Manager(object):
+class Manager:
     """Manage the parallelism and checker instances for each plugin and file.
 
     This class will be responsible for the following:
@@ -337,7 +340,7 @@ class Manager(object):
         self._process_statistics()
 
 
-class FileChecker(object):
+class FileChecker:
     """Manage running checks for a file and aggregate the results."""
 
     def __init__(self, filename, checks, options):
@@ -375,13 +378,13 @@ class FileChecker(object):
 
     def __repr__(self):  # type: () -> str
         """Provide helpful debugging representation."""
-        return "FileChecker for {}".format(self.filename)
+        return f"FileChecker for {self.filename}"
 
     def _make_processor(self):
         # type: () -> Optional[processor.FileProcessor]
         try:
             return processor.FileProcessor(self.filename, self.options)
-        except IOError as e:
+        except OSError as e:
             # If we can not read the file due to an IOError (e.g., the file
             # does not exist or we do not have the permissions to open it)
             # then we need to format that exception for the user.
diff --git a/src/flake8/exceptions.py b/src/flake8/exceptions.py
index e1b0539..bcc29de 100644
--- a/src/flake8/exceptions.py
+++ b/src/flake8/exceptions.py
@@ -24,7 +24,7 @@ class FailedToLoadPlugin(Flake8Exception):
         """Initialize our FailedToLoadPlugin exception."""
         self.plugin_name = plugin_name
         self.original_exception = exception
-        super(FailedToLoadPlugin, self).__init__(plugin_name, exception)
+        super().__init__(plugin_name, exception)
 
     def __str__(self):  # type: () -> str
         """Format our exception message."""
@@ -46,7 +46,7 @@ class InvalidSyntax(Flake8Exception):
         self.error_code = "E902"
         self.line_number = 1
         self.column_number = 0
-        super(InvalidSyntax, self).__init__(exception)
+        super().__init__(exception)
 
     def __str__(self):  # type: () -> str
         """Format our exception message."""
@@ -63,9 +63,7 @@ class PluginRequestedUnknownParameters(Flake8Exception):
         """Pop certain keyword arguments for initialization."""
         self.plugin = plugin
         self.original_exception = exception
-        super(PluginRequestedUnknownParameters, self).__init__(
-            plugin, exception
-        )
+        super().__init__(plugin, exception)
 
     def __str__(self):  # type: () -> str
         """Format our exception message."""
@@ -85,7 +83,7 @@ class PluginExecutionFailed(Flake8Exception):
         """Utilize keyword arguments for message generation."""
         self.plugin = plugin
         self.original_exception = exception
-        super(PluginExecutionFailed, self).__init__(plugin, exception)
+        super().__init__(plugin, exception)
 
     def __str__(self):  # type: () -> str
         """Format our exception message."""
diff --git a/src/flake8/formatting/base.py b/src/flake8/formatting/base.py
index ae78f49..89789b5 100644
--- a/src/flake8/formatting/base.py
+++ b/src/flake8/formatting/base.py
@@ -1,15 +1,16 @@
 """The base class and interface for all formatting plugins."""
-from __future__ import print_function
-
 import argparse
-from typing import IO, List, Optional, Tuple
+from typing import IO
+from typing import List
+from typing import Optional
+from typing import Tuple
 
 if False:  # `typing.TYPE_CHECKING` was introduced in 3.5.2
     from flake8.statistics import Statistics
     from flake8.style_guide import Violation
 
 
-class BaseFormatter(object):
+class BaseFormatter:
     """Class defining the formatter interface.
 
     .. attribute:: options
@@ -179,7 +180,7 @@ class BaseFormatter(object):
         )
         # Physical lines have a newline at the end, no need to add an extra
         # one
-        return "{}{}^".format(error.physical_line, indent)
+        return f"{error.physical_line}{indent}^"
 
     def _write(self, output):  # type: (str) -> None
         """Handle logic of whether to use an output file or print()."""
diff --git a/src/flake8/formatting/default.py b/src/flake8/formatting/default.py
index 55a5d01..0ff5a9b 100644
--- a/src/flake8/formatting/default.py
+++ b/src/flake8/formatting/default.py
@@ -1,5 +1,6 @@
 """Default formatting class for Flake8."""
-from typing import Optional, Set
+from typing import Optional
+from typing import Set
 
 from flake8.formatting import base
 
@@ -77,7 +78,7 @@ class FilenameOnly(SimpleFormatter):
         """Ensure we only print each error once."""
         if error.filename not in self.filenames_already_printed:
             self.filenames_already_printed.add(error.filename)
-            return super(FilenameOnly, self).format(error)
+            return super().format(error)
         else:
             return None
 
diff --git a/src/flake8/main/application.py b/src/flake8/main/application.py
index a247062..f5e3f10 100644
--- a/src/flake8/main/application.py
+++ b/src/flake8/main/application.py
@@ -1,11 +1,13 @@
 """Module containing the application logic for Flake8."""
-from __future__ import print_function
-
 import argparse
 import logging
 import sys
 import time
-from typing import Dict, List, Optional, Set, Tuple
+from typing import Dict
+from typing import List
+from typing import Optional
+from typing import Set
+from typing import Tuple
 
 import flake8
 from flake8 import checker
@@ -14,19 +16,21 @@ from flake8 import exceptions
 from flake8 import style_guide
 from flake8 import utils
 from flake8.main import options
-from flake8.options import aggregator, config
+from flake8.options import aggregator
+from flake8.options import config
 from flake8.options import manager
 from flake8.plugins import manager as plugin_manager
 
 if False:  # `typing.TYPE_CHECKING` was introduced in 3.5.2
     from typing import Type  # `typing.Type` was introduced in 3.5.2
+
     from flake8.formatting.base import BaseFormatter
 
 
 LOG = logging.getLogger(__name__)
 
 
-class Application(object):
+class Application:
     """Abstract our application into a class."""
 
     def __init__(self, program="flake8", version=flake8.__version__):
diff --git a/src/flake8/main/cli.py b/src/flake8/main/cli.py
index 1bc9155..9456ae2 100644
--- a/src/flake8/main/cli.py
+++ b/src/flake8/main/cli.py
@@ -1,6 +1,7 @@
 """Command-line implementation of flake8."""
 import sys
-from typing import List, Optional
+from typing import List
+from typing import Optional
 
 from flake8.main import application
 
diff --git a/src/flake8/main/debug.py b/src/flake8/main/debug.py
index 83a5a11..923c894 100644
--- a/src/flake8/main/debug.py
+++ b/src/flake8/main/debug.py
@@ -1,10 +1,9 @@
 """Module containing the logic for our debugging logic."""
-from __future__ import print_function
-
 import argparse
 import json
 import platform
-from typing import Dict, List
+from typing import Dict
+from typing import List
 
 
 class DebugAction(argparse.Action):
@@ -17,7 +16,7 @@ class DebugAction(argparse.Action):
         used to delay response.
         """
         self._option_manager = kwargs.pop("option_manager")
-        super(DebugAction, self).__init__(*args, **kwargs)
+        super().__init__(*args, **kwargs)
 
     def __call__(self, parser, namespace, values, option_string=None):
         """Perform the argparse action for printing debug information."""
diff --git a/src/flake8/main/options.py b/src/flake8/main/options.py
index fdde9e1..acadbb1 100644
--- a/src/flake8/main/options.py
+++ b/src/flake8/main/options.py
@@ -78,7 +78,7 @@ class JobsArgument:
             self.n_jobs = int(arg)
         else:
             raise argparse.ArgumentTypeError(
-                "{!r} must be 'auto' or an integer.".format(arg),
+                f"{arg!r} must be 'auto' or an integer.",
             )
 
     def __str__(self):
diff --git a/src/flake8/options/aggregator.py b/src/flake8/options/aggregator.py
index bdcd6a3..0ab7357 100644
--- a/src/flake8/options/aggregator.py
+++ b/src/flake8/options/aggregator.py
@@ -5,7 +5,8 @@ applies the user-specified command-line configuration on top of it.
 """
 import argparse
 import logging
-from typing import List, Tuple
+from typing import List
+from typing import Tuple
 
 from flake8.options import config
 from flake8.options.manager import OptionManager
diff --git a/src/flake8/options/config.py b/src/flake8/options/config.py
index 3dbaae7..dccc622 100644
--- a/src/flake8/options/config.py
+++ b/src/flake8/options/config.py
@@ -3,7 +3,9 @@ import collections
 import configparser
 import logging
 import os.path
-from typing import List, Optional, Tuple
+from typing import List
+from typing import Optional
+from typing import Tuple
 
 from flake8 import utils
 
@@ -12,7 +14,7 @@ LOG = logging.getLogger(__name__)
 __all__ = ("ConfigFileFinder", "MergedConfigParser")
 
 
-class ConfigFileFinder(object):
+class ConfigFileFinder:
     """Encapsulate the logic for finding and reading config files."""
 
     def __init__(
@@ -154,7 +156,7 @@ class ConfigFileFinder(object):
         return config
 
 
-class MergedConfigParser(object):
+class MergedConfigParser:
     """Encapsulate merging different types of configuration files.
 
     This parses out the options registered that were specified in the
diff --git a/src/flake8/options/manager.py b/src/flake8/options/manager.py
index 09bf862..5e0fee2 100644
--- a/src/flake8/options/manager.py
+++ b/src/flake8/options/manager.py
@@ -5,14 +5,23 @@ import contextlib
 import enum
 import functools
 import logging
-from typing import Any, Callable, cast, Dict, Generator, List, Mapping
-from typing import Optional, Sequence, Set, Tuple, Union
+from typing import Any
+from typing import Callable
+from typing import cast
+from typing import Dict
+from typing import Generator
+from typing import List
+from typing import Mapping
+from typing import Optional
+from typing import Sequence
+from typing import Set
+from typing import Tuple
+from typing import Union
 
 from flake8 import utils
 
 if False:  # TYPE_CHECKING
-    from typing import NoReturn
-    from typing import Type
+    from typing import NoReturn, Type
 
 LOG = logging.getLogger(__name__)
 
@@ -41,7 +50,7 @@ class _CallbackAction(argparse.Action):
         self._callback = kwargs.pop("callback")
         self._callback_args = kwargs.pop("callback_args", ())
         self._callback_kwargs = kwargs.pop("callback_kwargs", {})
-        super(_CallbackAction, self).__init__(*args, **kwargs)
+        super().__init__(*args, **kwargs)
 
     def __call__(
         self,
@@ -61,7 +70,7 @@ class _CallbackAction(argparse.Action):
             values,
             parser,
             *self._callback_args,
-            **self._callback_kwargs
+            **self._callback_kwargs,
         )
 
 
@@ -70,7 +79,7 @@ def _flake8_normalize(value, *args, **kwargs):
     comma_separated_list = kwargs.pop("comma_separated_list", False)
     normalize_paths = kwargs.pop("normalize_paths", False)
     if kwargs:
-        raise TypeError("Unexpected keyword args: {}".format(kwargs))
+        raise TypeError(f"Unexpected keyword args: {kwargs}")
 
     ret = value  # type: Union[str, List[str]]
     if comma_separated_list and isinstance(ret, utils.string_types):
@@ -85,7 +94,7 @@ def _flake8_normalize(value, *args, **kwargs):
     return ret
 
 
-class Option(object):
+class Option:
     """Our wrapper around an argparse argument parsers to add features."""
 
     def __init__(
@@ -284,7 +293,7 @@ class Option(object):
         for arg in self.option_args:
             parts.append(arg)
         for k, v in self.filtered_option_kwargs.items():
-            parts.append("{}={!r}".format(k, v))
+            parts.append(f"{k}={v!r}")
         return "Option({})".format(", ".join(parts))
 
     def normalize(self, value, *normalize_args):
@@ -337,7 +346,7 @@ PluginVersion = collections.namedtuple(
 )
 
 
-class OptionManager(object):
+class OptionManager:
     """Manage Options and OptionParser while adding post-processing."""
 
     def __init__(
diff --git a/src/flake8/plugins/manager.py b/src/flake8/plugins/manager.py
index 4f482dd..ab4cbd8 100644
--- a/src/flake8/plugins/manager.py
+++ b/src/flake8/plugins/manager.py
@@ -1,6 +1,10 @@
 """Plugin loading and management logic and classes."""
 import logging
-from typing import Any, Dict, List, Optional, Set
+from typing import Any
+from typing import Dict
+from typing import List
+from typing import Optional
+from typing import Set
 
 from flake8 import exceptions
 from flake8 import utils
@@ -13,7 +17,7 @@ __all__ = ("Checkers", "Plugin", "PluginManager", "ReportFormatters")
 NO_GROUP_FOUND = object()
 
 
-class Plugin(object):
+class Plugin:
     """Wrap an EntryPoint from setuptools and other logic."""
 
     def __init__(self, name, entry_point, local=False):
@@ -219,7 +223,7 @@ class Plugin(object):
             self.disable(optmanager)
 
 
-class PluginManager(object):  # pylint: disable=too-few-public-methods
+class PluginManager:  # pylint: disable=too-few-public-methods
     """Find and manage plugins consistently."""
 
     def __init__(self, namespace, local_plugins=None):
@@ -342,7 +346,7 @@ def version_for(plugin):
     return getattr(module, "__version__", None)
 
 
-class PluginTypeManager(object):
+class PluginTypeManager:
     """Parent class for most of the specific plugin types."""
 
     namespace = None  # type: str
diff --git a/src/flake8/plugins/pyflakes.py b/src/flake8/plugins/pyflakes.py
index e845483..5d51799 100644
--- a/src/flake8/plugins/pyflakes.py
+++ b/src/flake8/plugins/pyflakes.py
@@ -1,6 +1,4 @@
 """Plugin built-in to Flake8 to treat pyflakes as a plugin."""
-# -*- coding: utf-8 -*-
-from __future__ import absolute_import
 
 import os
 from typing import List
@@ -10,7 +8,6 @@ import pyflakes.checker
 
 from flake8 import utils
 
-
 FLAKE8_PYFLAKES_CODES = {
     "UnusedImport": "F401",
     "ImportShadowedByLoopVar": "F402",
@@ -96,7 +93,7 @@ class FlakesChecker(pyflakes.checker.Checker):
                 if overlaped_by:
                     with_doctest = True
 
-        super(FlakesChecker, self).__init__(
+        super().__init__(
             tree,
             filename=filename,
             withDoctest=with_doctest,
diff --git a/src/flake8/processor.py b/src/flake8/processor.py
index 8ace9a3..30c49ac 100644
--- a/src/flake8/processor.py
+++ b/src/flake8/processor.py
@@ -5,7 +5,12 @@ import contextlib
 import logging
 import sys
 import tokenize
-from typing import Any, Dict, Generator, List, Optional, Tuple
+from typing import Any
+from typing import Dict
+from typing import Generator
+from typing import List
+from typing import Optional
+from typing import Tuple
 
 import flake8
 from flake8 import defaults
@@ -25,7 +30,7 @@ _LogicalMapping = List[Tuple[int, Tuple[int, int]]]
 _Logical = Tuple[List[str], List[str], _LogicalMapping]
 
 
-class FileProcessor(object):
+class FileProcessor:
     """Processes a file and holdes state.
 
     This processes a file by generating tokens, logical and physical lines,
@@ -349,7 +354,7 @@ class FileProcessor(object):
 
     def _readlines_py2(self):
         # type: () -> List[str]
-        with open(self.filename, "rU") as fd:
+        with open(self.filename) as fd:
             return fd.readlines()
 
     def _readlines_py3(self):
diff --git a/src/flake8/statistics.py b/src/flake8/statistics.py
index 100227f..c238b8d 100644
--- a/src/flake8/statistics.py
+++ b/src/flake8/statistics.py
@@ -1,12 +1,15 @@
 """Statistic collection logic for Flake8."""
 import collections
-from typing import Dict, Generator, List, Optional
+from typing import Dict
+from typing import Generator
+from typing import List
+from typing import Optional
 
 if False:  # `typing.TYPE_CHECKING` was introduced in 3.5.2
     from flake8.style_guide import Violation
 
 
-class Statistics(object):
+class Statistics:
     """Manager of aggregated statistics for a run of Flake8."""
 
     def __init__(self):  # type: () -> None
@@ -102,7 +105,7 @@ class Key(collections.namedtuple("Key", ["filename", "code"])):
         )
 
 
-class Statistic(object):
+class Statistic:
     """Simple wrapper around the logic of each statistic.
 
     Instead of maintaining a simple but potentially hard to reason about
diff --git a/src/flake8/style_guide.py b/src/flake8/style_guide.py
index 9be0fe8..df2a036 100644
--- a/src/flake8/style_guide.py
+++ b/src/flake8/style_guide.py
@@ -7,8 +7,15 @@ import enum
 import itertools
 import linecache
 import logging
-from typing import Dict, Generator, List, Match, Optional, Sequence, Set
-from typing import Tuple, Union
+from typing import Dict
+from typing import Generator
+from typing import List
+from typing import Match
+from typing import Optional
+from typing import Sequence
+from typing import Set
+from typing import Tuple
+from typing import Union
 
 from flake8 import defaults
 from flake8 import statistics
@@ -142,7 +149,7 @@ class Violation(_Violation):
         return self.line_number in line_numbers
 
 
-class DecisionEngine(object):
+class DecisionEngine:
     """A class for managing the decision process around violations.
 
     This contains the logic for whether a violation should be reported or
@@ -318,7 +325,7 @@ class DecisionEngine(object):
         return decision
 
 
-class StyleGuideManager(object):
+class StyleGuideManager:
     """Manage multiple style guides for a single run."""
 
     def __init__(
@@ -437,7 +444,7 @@ class StyleGuideManager(object):
             guide.add_diff_ranges(diffinfo)
 
 
-class StyleGuide(object):
+class StyleGuide:
     """Manage a Flake8 user's style guide."""
 
     def __init__(
@@ -463,7 +470,7 @@ class StyleGuide(object):
 
     def __repr__(self):  # type: () -> str
         """Make it easier to debug which StyleGuide we're using."""
-        return "<StyleGuide [{}]>".format(self.filename)
+        return f"<StyleGuide [{self.filename}]>"
 
     def copy(self, filename=None, extend_ignore_with=None):
         # type: (Optional[str], Optional[Sequence[str]]) -> StyleGuide
@@ -499,7 +506,7 @@ class StyleGuide(object):
         return utils.matches_filename(
             filename,
             patterns=[self.filename],
-            log_message='{!r} does %(whether)smatch "%(path)s"'.format(self),
+            log_message=f'{self!r} does %(whether)smatch "%(path)s"',
             logger=LOG,
         )
 
diff --git a/src/flake8/utils.py b/src/flake8/utils.py
index 893571e..cd1b036 100644
--- a/src/flake8/utils.py
+++ b/src/flake8/utils.py
@@ -9,8 +9,16 @@ import platform
 import re
 import sys
 import tokenize
-from typing import Callable, Dict, Generator, List, Optional, Pattern
-from typing import Sequence, Set, Tuple, Union
+from typing import Callable
+from typing import Dict
+from typing import Generator
+from typing import List
+from typing import Optional
+from typing import Pattern
+from typing import Sequence
+from typing import Set
+from typing import Tuple
+from typing import Union
 
 from flake8 import exceptions
 from flake8._compat import lru_cache
@@ -21,7 +29,7 @@ if False:  # `typing.TYPE_CHECKING` was introduced in 3.5.2
 DIFF_HUNK_REGEXP = re.compile(r"^@@ -\d+(?:,\d+)? \+(\d+)(?:,(\d+))? @@.*$")
 COMMA_SEPARATED_LIST_RE = re.compile(r"[,\s]")
 LOCAL_PLUGIN_LIST_RE = re.compile(r"[,\t\n\r\f\v]")
-string_types = (str, type(u""))
+string_types = (str, type(""))
 
 
 def parse_comma_separated_list(value, regexp=COMMA_SEPARATED_LIST_RE):
@@ -204,18 +212,12 @@ def _stdin_get_value_py3():  # type: () -> str
 @lru_cache(maxsize=1)
 def stdin_get_value():  # type: () -> str
     """Get and cache it so plugins can use it."""
-    if sys.version_info < (3,):
-        return sys.stdin.read()
-    else:
-        return _stdin_get_value_py3()
+    return _stdin_get_value_py3()
 
 
 def stdin_get_lines():  # type: () -> List[str]
     """Return lines of stdin split according to file splitting."""
-    if sys.version_info < (3,):
-        return list(io.BytesIO(stdin_get_value()))
-    else:
-        return list(io.StringIO(stdin_get_value()))
+    return list(io.StringIO(stdin_get_value()))
 
 
 def parse_unified_diff(diff=None):