[Review] Request from 'tgoettlicher' @ 'SUSE/machinery/review_140805_'

Please review the following changes:
  * c70891a Show installation instructions for glance client on SLE12 if not installed
  * 6425d43 Merge branch 'fix-exception'
  * 5f42e71 Use correct exception
The message should make it clear that adding the module is not needed, when it's already there.