Comment 2 for bug 1733983

I haven't seen that warning message in a very long time. That is a feature in subunit-trace to warn about a bug we used to see quite frequently in testr: http://git.openstack.org/cgit/openstack/os-testr/tree/os_testr/subunit_trace.py#n303

What version of testr and os-testr are you running with. The most recent release of stestr should be immune from this because it doesn't actually use testr internally anymore (it switched to use stestr). But even if you were using os-testr < 1.0.0 if you're using a new enough version of testr that bug should have been fixed.