Applied on top of a pure run of black -l 79 in
I7eda77fed3d8e73df84b3651fd6cfcfe858d4dc9,  this set of changes
resolves all remaining flake8 conditions for those codes
we have enabled in setup.cfg.

Included are resolutions for all remaining flake8 issues
including shadowed builtins, long lines, import order, unused
imports, duplicate imports, and docstring issues.

Change-Id: I4f72d3ba1380dd601610ff80b8fb06a2aff8b0fe

This is a straight reformat run using black as is, with no edits
applied at all.

The black run will format code consistently, however in
some cases that are prevalent in SQLAlchemy code it produces
too-long lines.   The too-long lines will be resolved in the
following commit that will resolve all remaining flake8 issues
including shadowed builtins, long lines, import order, unused
imports, duplicate imports, and docstring issues.

Change-Id: I7eda77fed3d8e73df84b3651fd6cfcfe858d4dc9

Fixed bug where using :meth:`.Mutable.associate_with` or
:meth:`.Mutable.as_mutable` in conjunction with a class that has non-
primary mappers set up with alternatively-named attributes would produce an
attribute error.  Since non-primary mappers are not used for persistence,
the mutable extension now excludes non-primary mappers from its
instrumentation steps.

Change-Id: I2630d9f771a171aece03181ccf9159885f68f25e
Fixes: #4215
(cherry picked from commit 0fd508ad32a6f94653757a5ae10c1eae14e099fc)

Fixed regression in :class:`.ARRAY` datatype caused by
:ticket:`3964`, which is essentially the same
issue as that of :ticket:`3832`, where column attachment events
for :class:`.ARRAY` would not be invoked.   This breaks the use case
of using declarative mixins that declare a :class:`.Column` which
makes use of :meth:`.MutableList.as_mutable`.

Change-Id: If8c57615860883837f6cf72661e46180a77778c1
Fixes: #4141

Implemented in-place mutation operators ``__ior__``, ``__iand__``,
``__ixor__`` and ``__isub__`` for :class:`.mutable.MutableSet`
and ``__iadd__`` for :class:`.mutable.MutableList` so that change
events are fired off when these mutator methods are used to alter the
collection.

Change-Id: Ib357a96d3b06c5deb6b53eb304a8b9f1dc9e9ede
Fixes: #3853

Added new event handler :meth:`.AttributeEvents.modified` which is
triggered when the func:`.attributes.flag_modified` function is
invoked, which is common when using the :mod:`sqlalchemy.ext.mutable`
extension module.

Change-Id: Ic152f1d5c53087d780b24ed7f1f1571527b9e8fc
Fixes: #3303

Fixed regression released in 1.1.8 due to :ticket:`3950` where the
deeper search for information about column types in the case of a
"schema type" or a :class:`.TypeDecorator` would produce an attribute
error if the mapping also contained a :obj:`.column_property`.

Change-Id: I38254834d3d79c9b339289a8163eb4789ec4c931
Fixes: #3956

Fixed bug in :mod:`sqlalchemy.ext.mutable` where the
:meth:`.Mutable.as_mutable` method would not track a type that had
been copied using :meth:`.TypeEngine.copy`.  This became more of
a regression in 1.1 compared to 1.0 because the :class:`.TypeDecorator`
class is now a subclass of :class:`.SchemaEventTarget`, which among
other things indicates to the parent :class:`.Column` that the type
should be copied when the :class:`.Column` is.  These copies are
common when using declarative with mixins or abstract classes.

Change-Id: Ib04df862c58263185dbae686c548fea3e12c46f1
Fixes: #3950

tested using pycodestyle version 2.2.0

Fixes: #3885
Change-Id: I5df43adc3aefe318f9eeab72a078247a548ec566
Pull-request: https://github.com/zzzeek/sqlalchemy/pull/343

from https://bitbucket.org/zzzeek/sqlalchemy/issues/3297