Remove redundant exception assignations.

Remove some obvious assignations from the except clauses that do
not make any use of them.

Change-Id: I5521612493ee9d5a57816fbcd8a54b174d29aefb
Signed-off-by: Antoni S. Puimedon <asegurap@redhat.com>
Reviewed-on: http://gerrit.ovirt.org/11034
Reviewed-by: Igor Lvovsky <ilvovsky@redhat.com>
Reviewed-by: Ewoud Kohl van Wijngaarden <ewoud@kohlvanwijngaarden.nl>