Ignore warning from a known issue in flask-sqlalchemy in tests
Ignore warning from a known issue in flask-sqlalchemy in tests

flask-sqlalchemy tries to get all attributes of mixin class and
SQLAlchemy warns that it's not a good thing to do.

See https://github.com/mitsuhiko/flask-sqlalchemy/issues/349 for
details.

Change-Id: I7973fc2793fc74787b26f680cf596363f618900c

Mirantis/tuning-box