old_contents: module.exports = function (app) {
    app.all('*', function (req, res, next) {
      next('404: ' + req.url);
    });
  
    return function (err, req, res, next) {
      if (!err) return next();
      console.error(err.stack || err);
      var status = parseInt(err.message || err.toString());
      status = (status >= 400 && status < 600) ? status : 500;
      res.redirect('/' + status);
    };
  };
new_contents: module.exports = function (app) {
    app.all('*', function (req, res, next) {
      next('404: ' + req.url);
    });
  
    return function (err, req, res, next) {
      if (!err) return next();
      console.error(err.stack || err);
      var status = parseInt(err.message || err.toString());
      status = (status >= 400 && status < 600) ? status : 500;
      res.redirect('/error/' + status);
    };
  };
subject: add error prefix