Comment 6 for bug 1491325

Actually this isn't a problem in nova, device is optional, it's not nullable though. I have a change in tempest that attaches a volume and I don't specify device, it works fine:

http://logs.openstack.org/55/218355/6/check/gate-tempest-dsvm-nova-v21-full/03cdd7a/logs/tempest.txt.gz#_2015-09-02_17_32_14_204

So the bug is in novaclient passing device=None in the request.