around for a long time
- association proxy now returns None for proxied scalar that is also None, rather
than raising AttributeError. [ticket:2810]

scalar values, for comparisons to None to also take into account
the association record itself being non-present, in addition to the
existing test for the scalar endpoint on the association record
being NULL.  Previously, comparing ``Cls.scalar == None`` would return
records for which ``Cls.associated`` were present and
``Cls.associated.scalar`` is None, but not rows for which
``Cls.associated`` is non-present.  More significantly, the
inverse operation ``Cls.scalar != None`` *would* return ``Cls``
rows for which ``Cls.associated`` was non-present.

Additionally, added a special use case where you
can call ``Cls.scalar.has()`` with no arguments,
when ``Cls.scalar`` is a column-based value - this returns whether or
not ``Cls.associated`` has any rows present, regardless of whether
or not ``Cls.associated.scalar`` is NULL or not.
[ticket:2751]

- went through examples/ and cleaned out excess list() calls

now without strong ref on the parent
- fix message compare for py3k

become an externally usable package but still remains within the main sqlalchemy parent package.
in this system, we use kind of an ugly hack to get the noseplugin imported outside of the
"sqlalchemy" package, while still making it available within sqlalchemy for usage by
third party libraries.