Comment 5 for bug 1255419

Bumping requirement on stable/* doesn't look like a right approach, wasn't there a design session about freezing requirements on stable/* ?

Also iso8601>=0.1.8 didn't work on Grizzly when I tried it: https://review.openstack.org/53703
and then went with <=0.1.4 instead: https://review.openstack.org/55998