Add python-barbicanclient

Add python-barbicanclient, so that barbican can be
used by other openstack projects.  Specifically,
it is needed by nova and cinder for patches
https://review.openstack.org/#/c/104001/ and
https://review.openstack.org/#/c/104339/
to support cinder volume encryption using barbican
as the key manager.

Change-Id: I319f6cc834fb615f0a1c5aa22fabfbcff66ea771
Drop flake8 2.1.0

Complete the move to flake8 2.2.2

Change-Id: Ib3a202aadb979af449dbee3f99d04beda5f6e3e2
Update retrying to 1.2.2

Version 1.2.2 contains an important bug fix to not raise a RetryError
exception on failure when exceptions aren't being wrapped.

Change-Id: I5203bf833fd015e87245661262b91ff8d0badba5
Merge "Update retrying to 1.2.2"
Merge "Drop flake8 2.1.0"
Merge "Add python-barbicanclient"