decorator: Fix exception format for invalid API key.

This exception class was clearly missing the part where `role` gets
stored, which was intended to be inherited from
InvalidZulipServerError.

This fixes an unnecessary 500 error in the push notifications bouncer.

zerver/decorator.py

@@ -185,7 +185,7 @@ class InvalidZulipServerError(JsonableError):
     def msg_format() -> Text:
         return "Zulip server auth failure: {role} is not registered"
 
-class InvalidZulipServerKeyError(JsonableError):
+class InvalidZulipServerKeyError(InvalidZulipServerError):
     @staticmethod
     def msg_format() -> Text:
         return "Zulip server auth failure: key does not match role {role}"

zerver/tests/test_push_notifications.py

@@ -139,6 +139,18 @@ class PushBouncerNotificationTest(BouncerTestCase):
                                                                         'token': token})
         self.assert_json_error(result, "Must validate with valid Zulip server API key")
 
+        # We do a bit of hackery here to the API_KEYS cache just to
+        # make the code simple for sending an incorrect API key.
+        from zerver.lib.test_classes import API_KEYS
+        API_KEYS[self.server_uuid] = 'invalid'
+        result = self.api_post(self.server_uuid, endpoint, {'user_id': user_id,
+                                                            'token_kind': token_kind,
+                                                            'token': token})
+        self.assert_json_error(result, "Zulip server auth failure: key does not match role 1234-abcd",
+                               status_code=401)
+
+        del API_KEYS[self.server_uuid]
+
     def test_remote_push_user_endpoints(self) -> None:
         endpoints = [
             ('/api/v1/remotes/push/register', 'register'),