Comment 4 for bug 1346797

Reviewed: https://review.openstack.org/108659
Committed: https://git.openstack.org/cgit/openstack/cinder/commit/?id=64f6bebc6623a0e48dde3bef38390460728ea91e
Submitter: Jenkins
Branch: master

commit 64f6bebc6623a0e48dde3bef38390460728ea91e
Author: Marc Koderer <email address hidden>
Date: Tue Jul 22 13:53:45 2014 +0200

    Use abstract class for the backup driver interface

    Instead of using NotImplementedError exceptions to define the interface
    it's better to use python abc class [1]. The advantage that it fails
    faster if a class doesn't implement the needed interface.
    See also [2].

    [1]: http://legacy.python.org/dev/peps/pep-3119/
    [2]: http://dbader.org/blog/abstract-base-classes-in-python

    Change-Id: I625a73f70ac5c6ca68ee38a70c98d999454a817e
    Partial-Bug: #1346797