Updated openstack/openstack
Project: openstack/oslo.messaging  a704a3f1fcbb0e357d2fead8405c03c7586fa197

Use assertEqual instead of assertIs for strings

Checking identity of strings is not a great idea.
It might not work with different implementations. (eg. pypy)
Test usual equality instead.

Change-Id: Ib1a673a0ac116f2c80d066e94a8bd9a9ef8f518a