fix in return value for recv_msg

git-svn-id: svn://bind10.isc.org/svn/bind10/branches/f2f200910@169 e5f2f494-b856-4b98-b285-d166d9295462

src/lib/cc/python/ISC/CC/session.py

@@ -137,7 +137,9 @@ class Session:
     def group_recvmsg(self, nonblock = True):
         env = self.recvmsg(nonblock)
         if env == None:
-            return None
+            # return none twice to match normal return value
+            # (so caller won't get a type error on no data)
+            return (None, None)
         msg = Message.from_wire(env["msg"].encode('ascii'))
         return (msg, env)