According to Openstack summit session [1] stestr is
maintained project to which all Openstack projects
should migrate.
Let's switch it then.
[1] https://etherpad.openstack.org/p/YVR-python-pti
Also update requirements to pass gating.
Change-Id: Ibc8575f9f1c6084ec3e695c1ba5827b712aba318
Signed-off-by: Charles Short <zulcss@gmail.com>
Charles Short