code: public static CompletableFuture<Void> sendErrorResponse(
  			ChannelHandlerContext channelHandlerContext,
  			HttpRequest httpRequest,
  			ErrorResponseBody errorMessage,
  			HttpResponseStatus statusCode,
  			Map<String, String> headers) {
  
  		return sendErrorResponse(
  			channelHandlerContext,
  			HttpHeaders.isKeepAlive(httpRequest),
  			errorMessage,
  			statusCode,
  			headers);
  	}
docs: Sends the given error response and status code to the given channel.
  
  @param channelHandlerContext identifying the open channel
  @param httpRequest originating http request
  @param errorMessage which should be sent
  @param statusCode of the message to send
  @param headers additional header values