assert_diverge didn't really _assert_ before, this change causes it to exit if there are no differences from origin/$branch. Change-Id: I4b7d00425746c7f5eac4cfad20c89b75b38ac686 Reviewed-on: https://review.openstack.org/274 Reviewed-by: Monty Taylor <mordred@inaugust.com> Tested-by: Jenkins