2020 is coming, everyone should be using Python 3 now.
As per the official python support timeline set forth by the OpenStack
TC [1], OpenStack Train (in our case, kolla-ansible 9.x) is the last
release that will support python2.7.
[1] https://governance.openstack.org/tc/resolutions/20180529-python2-deprecation-timeline.html
Implements: blueprint drop-py2-support
Change-Id: Ibb3b12a779ecfd424053d0b3e98dac2f21d909bc
bindep installs a slew of stuff we don't really need and doesn't add
much if any value. This only turns on bindeps that are required.
This shaves about 3 minutes off each gate run.
Closes-Bug: #1620865
Change-Id: I24df4f2a30c682c1b09e89c7c52f7608582da1a6