Add new exception for invalid template ref

Hopefully is clearer than a KeyError.

Change-Id: Ib387825396ab0286df00aaff3b1b539cd7fc9a77
Fixes: bug #1178011
Use hostname from env in heat-keystone-setup

Prints a warning if the endpoints are going to be registered as localhost URIs.

Change-Id: I32efcf826f400ca2763cb5758dce02ffdbdb9ae1
Merge "Add new exception for invalid template ref"