Adding lintstack to support pylint testing.

* it should be carefully configured in future

Change-Id: I35f21e7fbfab3c5fa07cd3652f47469bb2939abd
Pin pbr to avoid sphinx autodocs issues

* https://review.openstack.org/#/c/32046/

Change-Id: I9254c735edfb555fb97dcec281d22d7fe6293c9e
Merge "Adding lintstack to support pylint testing."
Merge "Pin pbr to avoid sphinx autodocs issues"