Bug 1453760 - Fix commenter's check_needswork_owner() (#3874)

change logic so that it always updates whiteboard status,
unless whiteboard_needswork_owner already exists.

treeherder/intermittents_commenter/commenter.py

@@ -141,15 +141,17 @@ def check_needswork_owner(self, change_priority, bug_info, whiteboard):
                 change_priority = '--'
 
             stockwell_text = re.search(r'\[stockwell (.+?)\]', whiteboard)
-            if stockwell_text is not None and stockwell_text.group() != WHITEBOARD_NEEDSWORK_OWNER:
+            # update whiteboard text unless it already contains WHITEBOARD_NEEDSWORK_OWNER
+            if stockwell_text is None or stockwell_text.group() != WHITEBOARD_NEEDSWORK_OWNER:
                 whiteboard = self.update_whiteboard(whiteboard, WHITEBOARD_NEEDSWORK_OWNER)
 
         return change_priority, whiteboard
 
     def check_needswork(self, whiteboard):
         if whiteboard is not None:
             stockwell_text = re.search(r'\[stockwell (.+?)\]', whiteboard)
-            # covers all 'needswork' possibilities, ie 'needswork:owner'
+            # update all [stockwell needswork] bugs (including all 'needswork' possibilities,
+            # ie 'needswork:owner') and update whiteboard to [stockwell unknown]
             if stockwell_text is not None and stockwell_text.group(1).split(':')[0] == 'needswork':
                 whiteboard = self.update_whiteboard(whiteboard, '[stockwell unknown]')