Importing oslo_db.sqlalchemy and create_engine() issue

[Joshua Harlow]

It appears the following may be happening due to invalid imports/order?

>>> from oslo_db.sqlalchemy import engines
>>> u = "sqlite:////tmp/test.db"
>>> engines.create_engine(u, connection_trace=True)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "oslo_db/sqlalchemy/engines.py", line 139, in create_engine
    connection_trace=connection_trace
  File "oslo_db/sqlalchemy/utils.py", line 913, in __call__
    self._url_from_target(target), target, arg, kw)
  File "oslo_db/sqlalchemy/utils.py", line 950, in _dispatch_on
    return self._dispatch_on_db_driver(dbname, driver, arg, kw)
  File "oslo_db/sqlalchemy/utils.py", line 1004, in _dispatch_on_db_driver
    if self._invoke_fn(fn, arg, kw) is not None:
  File "oslo_db/sqlalchemy/utils.py", line 953, in _invoke_fn
    return fn(*arg, **kw)
  File "oslo_db/sqlalchemy/engines.py", line 227, in _init_events
    _add_trace_comments(engine)
  File "oslo_db/sqlalchemy/engines.py", line 381, in _add_trace_comments
    os.path.dirname(sys.modules['oslo_db.tests'].__file__),
KeyError: 'oslo_db.tests'

[Viktor Serhieiev (vsergeyev)]

Fix on review - https://review.openstack.org/#/c/221606/