Now that requirements.txt is at SQLAlchemy 0.9.7 at the minimum,
we can remove the engine_connect compatibility module as well
as part of the handle_error compatibility module.
In particular, this gives us the ability to add and remove
engine_connect events using the event API directly which
can be handy in test fixtures.
Change-Id: I48450ad9d472d4377913ad391a0f5e3ba0f1471f