and :func:`.event.listens_for`.  This is a convenience feature which
will wrap the given listener such that it is only invoked once.

level (e.g. on the :class:`.Mapper` or :class:`.ClassManager`
level, as opposed to on an individual mapped class, and also on
:class:`.Connection`) that also made use of internal argument conversion
(which is most within those categories) would fail to be removable.
fixes #2973

system would cause a recursion overflow due to usage of inspect.getargspec()
on it in order to detect a legacy calling signature for certain events,
and apparently there's no way to do this with a partial object.  Instead
we skip the legacy check and assume the modern style; the check itself
now only occurs for the SessionEvents.after_bulk_update and
SessionEvents.after_bulk_delete events.  Those two events will require
the new signature style if assigned to a "partial" event listener.
[ticket:2905]

into account the id() of the function itself and self, [ticket:2832]

provided via the :func:`.event.remove` function.
[ticket:2268]
- reorganization of event.py module into a package; with the addition of the
docstring work as well as the new registry for removal, there's a lot more code now.
the package separates concerns and provides a top-level doc for each subsection
of functionality
- the remove feature works by providing the EventKey object which associates
the user-provided arguments to listen() with a global, weak-referencing registry.
This registry stores a collection of _ListenerCollection and _DispatchDescriptor
objects associated with each set of arguments, as well as the wrapped function
which was applied to that collection.  The EventKey can then be recreated for
a removal, all the _ListenerCollection and _DispatchDescriptor objects are located,
and the correct wrapped function is removed from each one.

with @_legacy_signature, will inspect incoming listener functions
to see if they match an older signature, will wrap into a newer sig
- add an event listen argument named=True, will send all args as
kw args so that event listeners can be written with **kw, any combination
of names
- add a doc system to events that writes out the various calling styles
for a given event, produces deprecation messages automatically.
a little concerned that it's a bit verbose but will look at it up
on RTD for awhile to get a feel.
- change the calling signature for bulk update/delete events - we have
the BulkUD object right there, and there's at least six or seven things
people might want to see, so just send the whole BulkUD in
[ticket:2775]

actual mock objects from the mock library.  I'd like to use mock
for new tests so we might as well use it in obvious places.
- use unittest.mock in py3.3
- changelog
- add a note to README.unittests
- add tests_require in setup.py
- have tests import from sqlalchemy.testing.mock
- apply usage of mock to one of the event tests.  we can be using
this approach all over the place.

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

- Fixed potential memory leak which could occur if an
arbitrary number of :class:`.sessionmaker` objects
were created.   The anonymous subclass created by
the sessionmaker, when dereferenced, would not be garbage
collected due to remaining class-level references from the
event package.  This issue also applies to any custom system
that made use of ad-hoc subclasses in conjunction with
an event dispatcher.  Also in 0.7.10. [ticket:2650]

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.