Comment 2 for bug 1707273

Reviewed: https://review.openstack.org/488568
Committed: https://git.openstack.org/cgit/openstack/keystoneauth/commit/?id=81ec69116a5252c1f90c0a1742f88b409851b0a8
Submitter: Jenkins
Branch: master

commit 81ec69116a5252c1f90c0a1742f88b409851b0a8
Author: Monty Taylor <email address hidden>
Date: Fri Jul 28 13:45:25 2017 -0500

    Protect against missing interface attribute

    If deprecated options aren't registered, interface will not exist,
    resulting in NoSuchOptError.

    Add safeguards around accessing the interface opt, and appropriate test
    cases.

    Co-Authored-By: Eric Fried <email address hidden>
    Closes-Bug: #1707273
    Change-Id: Ic3df9817f0038f8f610db70d7e34fe9d458606b6