Could the error method of ReplyXxx be moved to trait Reply?

[mawenqi]

Can we add a new error method to the Reply trait, like
fn error(self, err: c_int);

This would allow multiple ReplyXxx types to share the same method implement, as they all currently have this method with identical signature and implement.
More important, it would enable the definition of a unified error handling function, like so:
fn handle_error(err: MyErrorType, reply: impl Reply)