Comment 6 for bug 1216851

Hmm, this seems to be an ordinary timeout exception that is raised if a test is executed for more than OS_TEST_TIMEOUT seconds (https://github.com/openstack/nova/blob/master/.testr.conf). And in case of migrations tests error messages can be very-very misleading. E.g. I can't run migrations tests in Nova on my machine without specifying OS_TEST_TIMEOUT=0, because it takes more than 160 seconds to tun test_walk_versions() for MySQL.

The more migrations we put to Nova, the more often we face this issue (depending on the load of CI nodes of course).

So I would suggest to increase the OS_TEST_TIMEOUT value (or turn it off for migrations tests, if it's possible)