Follow in the footsteps of fedora-infra/fedmsg#173.
Merge pull request #35 from fedora-infra/feature/idempotency-following-suit

Follow in the footsteps of fedora-infra/fedmsg#173.
Merge branch 'develop' into feature/scm-old-message-bugfix
Somehow this got left out of one of the merges.
Merge branch 'develop' of github.com:fedora-infra/fedmsg_meta_fedora_infrastructure into feature/scm-old-message-bugfix
Add test suite to cover older SCM messages without username specified