Reinstate pure-git-hashes-are-illegal test.
Reinstate pure-git-hashes-are-illegal test.

When we removed output support for git hashes we also removed parsing
support for them. This would be ok (but rough on users), except that
we also removed the test that a pure git hash is an illegal version,
which should have stayed.

Change-Id: Idd8bc470fab1711d8555a793b1294b0977ba106d

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