code: protected Mono<ServerResponse> renderErrorView(ServerRequest request) {
  		boolean includeStackTrace = isIncludeStackTrace(request, MediaType.TEXT_HTML);
  		Map<String, Object> error = getErrorAttributes(request, includeStackTrace);
  		HttpStatus errorStatus = getHttpStatus(error);
  		ServerResponse.BodyBuilder responseBody = ServerResponse.status(errorStatus)
  				.contentType(MediaType.TEXT_HTML);
  		return Flux
  				.just("error/" + errorStatus.value(),
  						"error/" + SERIES_VIEWS.get(errorStatus.series()), "error/error")
  				.flatMap((viewName) -> renderErrorView(viewName, responseBody, error))
  				.switchIfEmpty(this.errorProperties.getWhitelabel().isEnabled()
  						? renderDefaultErrorView(responseBody, error)
  						: Mono.error(getError(request)))
  				.next();
  	}
docs: Render the error information as an HTML view.
  @param request the current request
  @return a {@code Publisher} of the HTTP response