packaging: setup: handling exception from uuid validation

Better handling of exception from UUID validation
to provide an easier to read and more consistent error.

Change-Id: I505a4f01d41c218a572f6e42682b57875712f1c0
Bug-Url: https://bugzilla.redhat.com/1125834
Signed-off-by: Simone Tiraboschi <stirabos@redhat.com>