def execute_undo(self, message):
info("<STR_LIT>")<EOL>with self.world._unlock_temporarily():<EOL><INDENT>message._undo(self.world)<EOL>self.world._react_to_undo_response(message)<EOL><DEDENT>for actor in self.actors:<EOL><INDENT>actor._react_to_undo_response(message)<EOL><DEDENT>
Manage the response when the server rejects a message.

An undo is when required this client sends a message that the server 
refuses to pass on to the other clients playing the game.  When this 
happens, the client must undo the changes that the message made to the 
world before being sent or crash.  Note that unlike sync requests, undo 
requests are only reported to the client that sent the offending 
message.