Updated openstack/openstack
Project: openstack/oslo.db  cb55c6171727a39fedb5b7526c801b91c99b641f

Opportunistic migration tests

Migrations should be tested with real database backends. For this goal
intended number of base test cases which used in current implementation.
Previously there were two ways to run migration tests: using
opportunistic test cases (default way we've been using on CI) and
by using database connection strings, specified in test_migrations.conf,
for every particular database test case. For the sake of simplicity and
consistency we are moving to using of opportunistic db test cases here.

With this change we are free from locking, so we don't need `lockfile`
anymore.

Closes-Bug: #1327397
Closes-Bug: #1328997
Change-Id: I92b1dcd830c4755f429a0f6529911e607c2c7de7