Comment 12 for bug 840641

Okay, I asked the Ubuntu maintainer (Dave Walker) and he pointed me to this:

  https://bugs.launchpad.net/ubuntu/+source/nova/+bug/840641

and they used this patch to fix their issue:

  https://bitbucket.org/ambroff/greenlet/changeset/2d5b17472757/raw/

certainly seems like the right area of code