(e.g. ``x[:] = [...]``) would fail on Py3k.

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.

caused a user-provided "getter" to no longer receive values of ``None``
when fetching scalar values from a target that is non-present.  The
check for None introduced by this change is now moved into the default
getter, so a user-provided getter will also again receive values of
None.
re: #2810

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.

new automap extension would fail if classes
were pre-arranged in single or potentially joined inheritance patterns.
The repaired joined inheritance issue could also potentially apply when
using :class:`.DeferredReflection` as well.

target of :paramref:`.relationship.secondary` for the purposes
of creating very complex :func:`.relationship` join conditions.
The change includes adjustments to query joining, joined eager loading
to not render a SELECT subquery, changes to lazy loading such that
the "secondary" target is properly included in the SELECT, and
changes to declarative to better support specification of a
join() object with classes as targets.

:class:`.DeferredReflection`
to define classes pending for reflection, if some subset of those
classes were discarded before the :meth:`.DeferredReflection.prepare`
method were called to reflect and map the class, a strong reference
to the class would remain held within the declarative internals.
This internal collection of "classes to map" now uses weak
references against the classes themselves.

attribute on declarative to simply refer directly to an :class:`.InstrumentedAttribute`
on a superclass or on the class itself, and it
acts more or less like a synonym; in 0.9, this fails to set up enough
bookkeeping to keep up with the more liberalized backref logic
from :ticket:`2789`.  Even though this use case was never directly
considered, it is now detected by declarative at the "setattr()" level
as well as when setting up a subclass, and the mirrored/renamed attribute
is now set up as a :func:`.synonym` instead. [ticket:2900]

:class:`.Column` is mapped multiple times under different properties
(which typically should be a :func:`.synonym` instead) or if two
or more :class:`.Column` objects are given the same name, raising
a warning if this condition is detected. [ticket:2828]