Replaced 404 response with 204 (empty)

For subscriptions that do not yet exist, return a 204 `NO CONTENT`
response instead of a 404 `NOT FOUND`. Backbone handles empty reponses
correctly, and the 204 code will not trigger a jQuery `ajaxError` event.

Author: schwuk

code_comments/subscription.py

@@ -481,9 +481,7 @@ def filter_stream(self, req, method, filename, stream, data):
     def _do_GET(self, req):
         subscription = Subscription.for_request(self.env, req)
         if subscription is None:
-            raise HTTPNotFound('Subscription to /%s%s for %s not found',
-                               req.args.get('realm'), req.args.get('path'),
-                               req.authname)
+            req.send('', 'application/json', 204)
         req.send(json.dumps(subscription, cls=SubscriptionJSONEncoder),
                  'application/json')