Comment 22 for bug 1812935

Looking at https://bugs.launchpad.net/cloud-archive/+bug/1812672 it appears this only happens with eventlet monkey patching in force, which explains why it doesn't reproduce in our unit tests.

I've come up with what appears to be a backportable fix (read: hack) in https://review.openstack.org/639457 I don't fully understand why one thing works in one environment and another thing in a different one, but it works (for a unit test version of "works") in the various combinations of Python and eventlet that I've tried.

Ideally we would merge that before the pymemcache switch and then rip it all out again in favor of pymemcache as soon as the backports are proposed.