Preparing for removal of six.reraise()
Preparing for removal of six.reraise()

Add unit tests to make sure the behavior of two functions using
six.rereaise() will be the same once six usage is removed.

Change-Id: Ie75beeb3f52aac26757500b39b76f2811ff97ac9

openstack/cinder,openstack/cinder,mahak/cinder,mahak/cinder