Comment 5 for bug 1410235

Reviewed: https://review.openstack.org/158364
Committed: https://git.openstack.org/cgit/openstack/nova/commit/?id=d240b281129111d568d420d64450bbd0aac7a561
Submitter: Jenkins
Branch: master

commit d240b281129111d568d420d64450bbd0aac7a561
Author: Roman Podoliaka <email address hidden>
Date: Mon Feb 23 19:12:34 2015 +0200

    Fix the order of base classes in migrations test cases

    Next release of oslo.db is going to break Nova migrations tests: when
    a test case cleanup is run it fails to fetch 'schema' attribute of
    oslo.db base test case sets in its setup. The problem is that Nova
    base test case intentionally removes all attributes from a test case
    class instance in its cleanup callback (to ensure there are no memory
    leaks).

    Inheritance from Nova base test case was actually added when fixing
    LP #1410235, so that TIMEOUT_SCALING_FACTOR attribute would be
    handled properly (at that time it was done directly in Nova base test
    case setUp(), and now it's a separate fixture).

    So in order for Nova unit tests to work correctly with new release of
    oslo.db we need either to remove inheritance from Nova base test case
    or to change the order of base classes to achieve the 'proper' MRO
    for migration test cases. The latter can actually be problematic as
    we also need to ensure TIMEOUT_SCALING_FACTOR is still handled
    properly and not overridden by oslotest base test case.

    Related-Bug: #1410235

    Change-Id: I5c7d2a391425766a5e8fd61a532b1a1e7d410770