The test system has removed support for Nose, which is unmaintained for
several years and is producing warnings under Python 3. The test suite is
currently standardized on Pytest.  Pull request courtesy Parth Shandilya.

Fixes: #4460

Closes: #4476
Pull-request: https://github.com/sqlalchemy/sqlalchemy/pull/4476
Pull-request-sha: e857af9c7d07355e52841149ee2e5d4448409e1e

Change-Id: I76516fae1cf0eb58f2e9fc9f692e591e0fcf39a4

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

the "./lib" prefix is again inserted at the head of sys.path but
only if sys.flags.no_user_site isn't set; this makes it act just
like the way Python puts "." in the current path by default.
For tox, we are setting the PYTHONNOUSERSITE flag now.
fixes #3356

it for the plain "pytest" case, so do an append instead of an insert
- add a new tox file to do a full regen of callcounts

- reestablish the "bootstrap" system of loading the test runners
in testing/plugin; using the updated approach we just came up with for
alembic.  Coverage should be fixed now when running either py.test or
nose. fixes #3196
- upgrade tox.ini and start using a .coveragerc file

part of #2830

let's stay on the fence.

is currently being supported in addition to nose, and will likely
be preferred to nose going forward.   The nose plugin system used
by SQLAlchemy has been split out so that it works under pytest as
well.  There are no plans to drop support for nose at the moment
and we hope that the test suite itself can continue to remain as
agnostic of testing platform as possible.  See the file
README.unittests.rst for updated information on running tests
with pytest.

The test plugin system has also been enhanced to support running
tests against mutiple database URLs at once, by specifying the ``--db``
and/or ``--dburi`` flags multiple times.  This does not run the entire test
suite for each database, but instead allows test cases that are specific
to certain backends make use of that backend as the test is run.
When using pytest as the test runner, the system will also run
specific test suites multiple times, once for each database, particularly
those tests within the "dialect suite".   The plan is that the enhanced
system will also be used by Alembic, and allow Alembic to run
migration operation tests against multiple backends in one run, including
third-party backends not included within Alembic itself.
Third party dialects and extensions are also encouraged to standardize
on SQLAlchemy's test suite as a basis; see the file README.dialects.rst
for background on building out from SQLAlchemy's test platform.