title: username or password failure message in Passport.js
body: <p>I have a login created in Express with the use of Passport.js. Now I have everything setup and when username and password are correct it will redirect to the user page. But now I want to show a message when the credentials are incorrect. Right now it leads to a blank page with an auto message of 'unauthorized'</p>
  
  <p>This is my passport.js setup:</p>
  
  <p>App.js:</p>
  
  <pre><code>var mongoose = require('mongoose');
  mongoose.Promise = global.Promise;
  mongoose.connect('mongodb://localhost:27017/homeapp');
  
  var passport = require('passport');
  var LocalStrategy = require('passport-local').Strategy;
  
  app.use(require('express-session')({
    secret: 'testtest',
    resave: false,
    saveUninitialized: false
  }));
  app.use(passport.initialize());
  app.use(passport.session());
  var User = require('./models/User');
  passport.use(new LocalStrategy(User.authenticate()));
  passport.serializeUser(User.serializeUser());
  passport.deserializeUser(User.deserializeUser());
  </code></pre>
  
  <p>Index.js</p>
  
  <pre><code>var express = require('express');
  var router = express.Router();
  var auth = require('../controller/AuthController.js');
  
  router.get('/', auth.home);
  
  router.get('/login', auth.login);
  
  router.post('/login', auth.doLogin);
  
  router.get('/logout', auth.logout);
  
  module.exports = router;
  </code></pre>
  
  <p>Users.js:</p>
  
  <pre><code>var mongoose = require('mongoose');
  var Schema = mongoose.Schema;
  var passportLocalMongoose = require('passport-local-mongoose');
  
  var UserSchema = new Schema({
      username: String,
      password: String
  }, {collection: 'userdata'});
  
  UserSchema.plugin(passportLocalMongoose);
  
  module.exports = mongoose.model('User', UserSchema);
  </code></pre>
  
  <p>AuthController.js:</p>
  
  <pre><code>var mongoose = require("mongoose");
  var passport = require("passport");
  var User = require("../models/User");
  
  var userController = {};
  
  userController.home = function(req, res) {
    res.render('index', { user : req.user });
  };
  
  userController.login = function(req, res) {
    res.render('login');
  };
  
  userController.doLogin = function(req, res){
    passport.authenticate('local')(req, res, function(){
      res.redirect('/');
    });
  };
  
  userController.logout = function(req, res) {
    req.logout();
    res.redirect('/');
  };
  
  module.exports = userController;
  </code></pre>