Comment 10 for bug 1255419

So let's try C. although I don't think bumping required versions of dependencies on stable is a good idea in general, but we need to unblock stable/grizzly somehow.

I've restored https://review.openstack.org/55939 and tests pass now, but I'm not sure if that's enough to declare grizzly Glance is fully working with iso8601 - I'll add more Glance floks as reviewers.