Updated openstack/openstack
Project: openstack/oslo.config  e57aea86c54060d22cc04dd88a4c4feea614d4e4

Add pbr to installation requirements

Add pbr to the list of installation requirements so that it is installed
via pip before this library is installed, instead of with easy_install.
This avoids issues like Bug #1384919, and ensures that projects that use
this library as a dependency are properly installed.

Change-Id: I6c155370dbd01fe4748d5137bdf288e8d3e1a67e