Add test for security error with no message
Add test for security error with no message

A test is added that shows that when no message is given to a
SecurityError the resulting string is the same whether debug
is enabled or not, it's just got some extra text that says that
disabling debug will change the message when it won't.

Change-Id: I40c899e48205e27e46a9af709fe94ef92492e0c0
Partial-Bug: 1496530

himanshu-setia/keystone,himanshu-setia/keystone,dims/keystone,cernops/keystone,klmitch/keystone,mahak/keystone,ilay09/keystone,mahak/keystone,klmitch/keystone,rajalokan/keystone,mahak/keystone,dims/keystone,cernops/keystone,openstack/keystone,rajalokan/keystone,ilay09/keystone,openstack/keystone,openstack/keystone,ilay09/keystone,rajalokan/keystone