In this change [1] os_testr changed under the covers from using
testr to stestr, so that we now get the following warning:
ostestr.py:120:
UserWarning: No .stestr.conf file found in the CWD.
Please create one to to replace the .testr.conf. You can find a
script to do this in the stestr git repository.
So remove the .testr.conf and add .stestr.conf which was
generated using a utility script as documented here [2].
[1] Id7cb2a39a8308f1413608dcf19273a1d7f33592e
[2] https://media.readthedocs.org/pdf/stestr/stable/stestr.pdf
TrivialFix
Change-Id: I6bb369624c4a790242022e203e771a77ffe06cf5