Updated openstack/openstack
Project: openstack/requirements  a41201f0be37117fe9f9d90a1e478ed3389c6e28

Bump up to the six 1.7.x series

The six 1.7.x series brings in some nice adjustments
that users of six can take advantage of, including
but not limited to (the below were selected from
the six changelog and are widely used six features
across openstack):

- Select the implementations of dictionary iterator
  routines at import time for a 20% speed boost.
- Improve add_metaclass, so that it doesn't end up
  inserting another class into the hierarchy.

The full changelog can be found at:

https://bitbucket.org/gutworth/six/src/35f6/CHANGES?at=1.7.0

Change-Id: I80b09c5921ad277e1ec1da47ae718db8b43a8c23