
Python 3.6 and 3.7 are not supported any of active stable branches now, so no longer need to be supported. Also remove Python 3.8 support according to [1]. [1] https://lists.openstack.org/archives/list/openstack-discuss@lists.openstack.org/thread/FOWV4UQZTH4DPDA67QDEROAESYU5Z3LE/ Also add a few new versions currently tested. Change-Id: I2773938f4e7c4db213e9435fbf7ceaa6e0887f43