private void deliverError(Message msg, int errCode, String errMsg) {
        Reply reply = new EmptyReply();
        reply.swapState(msg);
        reply.addError(new Error(errCode, errMsg));
        deliverReply(reply, reply.popHandler());
    }
<p>Constructs and schedules a Reply containing an error to the handler of the given Message.</p>

@param msg     The message to reply to.
@param errCode The code of the error to set.
@param errMsg  The message of the error to set.
messagebus/src/main/java/com/yahoo/messagebus/MessageBus.java