koji-wrapper: Handle failed subtasks

If a subtask fails, we can't ask about it's results as that would raise
an exception. We can safely assume that since the parent succeeded, any
failed child is actually allowed to fail.

Fixes: #641
Signed-off-by: Lubomír Sedlář <lsedlar@redhat.com>

pungi/wrappers/kojiwrapper.py

@@ -354,6 +354,11 @@ class KojiWrapper(object):
             if child_task['method'] not in ['createImage', 'createLiveMedia', 'createAppliance']:
                 continue
 
+            if child_task['state'] != koji.TASK_STATES['CLOSED']:
+                # The subtask is failed, which can happen with the can_fail
+                # option. Let's ignore it then.
+                continue
+
             is_scratch = child_task['request'][-1].get('scratch', False)
             task_result = self.koji_proxy.getTaskResult(child_task['id'])