Moving all OAuth code and samples to use Storage consistently
diff --git a/samples/oauth2/latitude/latitude.py b/samples/oauth2/latitude/latitude.py
index fc312dd..e0458f4 100644
--- a/samples/oauth2/latitude/latitude.py
+++ b/samples/oauth2/latitude/latitude.py
@@ -26,7 +26,7 @@
   storage = Storage('latitude.dat')
   credentials = storage.get()
 
-  if not credentials:
+  if credentials is None or credentials.invalid:
     flow = OAuth2WebServerFlow(
         client_id='433807057907.apps.googleusercontent.com',
         client_secret='jigtZpMApkRxncxikFpR+SFg',