According to Openstack summit session [1],
stestr is maintained project to which all Openstack projects should migrate.
Let's switch to stestr as other projects have already moved to it.
[1] https://etherpad.openstack.org/p/YVR-python-pti
Change-Id: I99bef7040974e193bc5a57f6f5a7dd7fe293519d
Usually, coverage report is created by "tox -ecover" command.
But it wasn't created. This fixes it.
Change-Id: If1096d70831e055d9d1f77a2fd08d28025c18597
Closes-Bug: #1374259