To mimic the common filter of the same name, but for the python tests.

Signed-off-by: John Snow <jsnow@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20181221093529.23855-7-jsnow@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>