pbr/testr_command.py: Add logging
pbr/testr_command.py: Add logging

to aid in debugging and testing.

Change-Id: I5342604204602623cdb5c0f2623d85f7d44e2b50

varunarya10/pbr,klmitch/pbr,varunarya10/pbr,klmitch/pbr,JioCloud/pbr,WiFast/pbr,openstack-dev/pbr,openstack-dev/pbr,redhat-openstack/pbr,JioCloud/pbr,redhat-openstack/pbr,WiFast/pbr,openstack-dev/pbr