is going to be trivial, with adding an option for this ( copy+paste
from
 the EPEL config ), and then finding a way to yum install
 centos-release-openstack-<ver> and if not found, yum install
 <rdo-release>; that should cover us for folks on CentOS Linux or not. 
Please no more options :) EPEL option must actually be removed, I'll
file another blocker for that.
It should be automatic, like rdo-release handling: if host running
packstack has centos-release-openstack-* installed, install it on other
nodes.
Cheers,
Alan