and also will fail on py3k.
- enhance exclusions so that a requirement attribute can be passed
to fails_if/skip_if.
- fix coverage docs to mention pytest.

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.

- break out reflection of views to support view column reflection separately
from view definition

both _resolve_type_affinity() directly as well as round trip tests fully.

fully usable within declarative relationship configuration, as its
string classname would not be available in the registry of classnames
at mapper configuration time.   The class now explicitly adds itself
to the class regsitry, and additionally both :class:`.AbstractConcreteBase`
as well as :class:`.ConcreteBase` set themselves up *before* mappers
are configured within the :func:`.configure_mappers` setup, using
the new :meth:`.MapperEvents.before_configured` event. [ticket:2950]

- Added new :meth:`.MapperEvents.before_configured` event which allows
an event at the start of :func:`.configure_mappers`, as well
as ``__declare_first__()`` hook within declarative to complement
``__declare_last__()``.

- modified how after_configured is invoked; we just make a dispatch()
not actually connected to any mapper.  this makes it easier
to also invoke before_configured correctly.

- improved the ComparableEntity fixture to handle collections that are sets.