to get all flake8 passing

in all cases unconditionally, the number of use cases that go beyond what
dbapi_error() is expecting has gone too far for an 0.9 release.
Additionally, the number of things we'd like to track is really a lot
more than the five arguments here, and ExecutionContext is really not
suitable as totally public API for this.   So restore dbapi_error
to its old version, deprecate, and build out handle_error instead.
This is a lot more extensible and doesn't get in the way of anything
compatibility-wise.

have been enhanced such that the function handler is now capable
of raising or returning a new exception object, which will replace
the exception normally being thrown by SQLAlchemy.
fixes #3076

Found using: https://github.com/intgr/topy

implementation allows an event handler to redefine the specific mechanics
by which an arbitrary dialect invokes execute() or executemany() on a
DBAPI cursor.  The new events, at this point semi-public and experimental,
are in support of some upcoming transaction-related extensions.

events including auto-invalidation, which is useful both for tests here as well as
detecting failure conditions within the "reset" or "close" cases.
- rename the argument for PoolEvents.reset() to dbapi_connection and connection_record
to be consistent with everything else.
- add new documentation sections on invalidation, including auto-invalidation
and the invalidation process within the pool.
- add _ConnectionFairy and _ConnectionRecord to the pool documentation.  Establish
docs for common _ConnectionFairy/_ConnectionRecord methods and accessors and
have PoolEvents docs refer to _ConnectionRecord,
since it is passed to all events.  Rename a few _ConnectionFairy methods that are actually
private to pool such as _checkout(), _checkin() and _checkout_existing(); there should not
be any external code calling these

- rework the event system so that event modules load after their
targets, dependencies are reversed
- create an improved strategy lookup system for the ORM
- rework the ORM to have very few import cycles
- move out "importlater" to just util.dependency
- other tricks to cross-populate modules in as clear a way as possible