[IMP] auth_oauth: doc improvement

bzr revid: rco@openerp.com-20121127100635-vzbuw6a73286t2t2

addons/auth_oauth/res_users.py

@@ -51,6 +51,7 @@ class res_users(osv.Model):
             :param validation: result of validation of access token (dict)
             :param params: oauth parameters (dict)
             :return: user login (str)
+            :raise: openerp.exceptions.AccessDenied if signin failed
 
             This method can be overridden to add alternative signin methods.
         """