Comment 2 for bug 1694509

Yeah I've seen this twice this week:

http://logs.openstack.org/49/483149/2/check/gate-novaclient-dsvm-functional-neutron-ubuntu-xenial/d37b26f/logs/screen-c-vol.txt.gz#_Jul_13_20_07_49_514341

Apparently it happens a lot:

http://logstash.openstack.org/#dashboard/file/logstash.json?query=message%3A%5C%22error%3A%20cannot%20switch%20to%20a%20different%20thread%5C%22%20AND%20tags%3A%5C%22screen-c-vol.txt%5C%22&from=7d

but it's not always related to an error - but I have seen cases where a volume fails to be created or at least report that it's created so tests just timeout and fail.