code: function (res, errorCode, errorMessage) {
      res.writeHead(errorCode, {"Content-Type": "text/html"});
      //Read the local error file
      return fs.readFile(options.error, "utf8", function (error, content) {
          //Check the error
          if (error) {
              return res.end("<" + "h1>Error</h1><p>" + errorMessage + "</p>");
          }
          let data = {code: errorCode, message: errorMessage};
          content = content.replace(/{{([^{}]+)}}/g, function(match, found)
              {
                  found = found.trim();
                  if(typeof data[found] !== "undefined") {
                      return data[found].toString();
                  } else {
                      return match;
                  }
              });
          return res.end(content);
      });
  }
docs: Display an error page