Add OAuth2 support for end users (i.e. 3-legged flow with the browser).

third_party/oauth2client/multistore_file.py

Index: third_party/oauth2client/multistore_file.py
diff --git a/third_party/oauth2client/multistore_file.py b/third_party/oauth2client/multistore_file.py
index ce7a5194feddfe92718fcc56de46e9a795408afc..31bf576a48f69b8d1a7573120533741e1a8f4f5c 100644
--- a/third_party/oauth2client/multistore_file.py
+++ b/third_party/oauth2client/multistore_file.py
@@ -50,9 +50,9 @@ import os
 import threading
 
 from anyjson import simplejson
-from oauth2client.client import Storage as BaseStorage
-from oauth2client.client import Credentials
-from oauth2client import util
+from client import Storage as BaseStorage
+from client import Credentials
+from . import util
 from locked_file import LockedFile
 
 logger = logging.getLogger(__name__)