Comment 6 for bug 1097203

Seems to be fixed upstream in greenlet-0.3.2

https://github.com/python-greenlet/greenlet/commit/2f81f5d

It probably makes sense to require 0.3.2 to ensure we have this behaviour

Distros which are still shipping 0.3.1 (nearly 3 years old!) may choose to backport the fix though