private void replyError(SendContext ctx, int errCode, String errMsg) {
        for (RoutingNode recipient : ctx.recipients) {
            Reply reply = new EmptyReply();
            reply.getTrace().setLevel(ctx.traceLevel);
            reply.addError(new Error(errCode, errMsg));
            recipient.handleReply(reply);
        }
    }
Deliver an error reply to the recipients of a {@link SendContext} in a way that avoids entanglement.

@param ctx     the send context that contains the recipient data
@param errCode the error code to return
@param errMsg  the error string to return
messagebus/src/main/java/com/yahoo/messagebus/network/rpc/RPCNetwork.java