Hi See here: https://review.openstack.org/20026 We currently require greenlet>=0.3.1 and 0.3.1 is almost 3 years old. It's the version in Fedora 18 and Ubuntu Precise. 0.3.2 has a fix for a nasty issue found with Oslo's thread group. Ubuntu Quantal has 0.3.3. The latest version is 0.4.0. Cheers, Mark.