WPT Export: trim lines from branch list, stage changes before committing

third_party/WebKit/Tools/Scripts/webkitpy/w3c/wpt_github.py

 # Copyright 2016 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 import base64
 import json
 import logging
 import os
 import sys
 import urllib2
@@ skipping 78 matching lines @@
         path = '/repos/w3c/web-platform-tests/pulls/%d/merge' % pull_request_number
         body = {}
         data, status_code = self.request(path, method='PUT', body=body)
 
         if status_code == 200:
             return data
         else:
             raise Exception('PR could not be merged: %d' % pull_request_number)
 
     def delete_remote_branch(self, remote_branch_name):
+        # TODO(jeffcarp): Unit test this method
         path = '/repos/w3c/web-platform-tests/git/refs/heads/%s' % remote_branch_name
         data, status_code = self.request(path, method='DELETE')
 
-        if status_code != 200:
+        if status_code != 204:
             # TODO(jeffcarp): Raise more specific exception (create MergeError class?)
-            raise Exception('PR could not be merged')
+            raise Exception('Received non-204 status code attempting to delete remote branch: {}'.format(status_code))
 
         return data