Open Stack

At the BCN summit, one of the suggestions for enabling Python 3 in
devstack was to provide an explicit whitelist of services that
should be run under Python 3. The first phase of that is in [1],
which adds both a white and black list.  The automatic detection
using the python classifiers is retained, for now, until we can
either (a) decide if we still want to drop it or (b) update any
existing test jobs to use the new whitelist feature to avoid breaking
them.

The patch in [2] is a related change to ensure that all libraries
listed in LIBS_FROM_GIT are installed under both Python 2 and Python
3 so the version being edited is tested in all cases.

Doug

[1] https://review.openstack.org/418125
[2] https://review.openstack.org/418135