How to redirect to a page on an error in passport-local

How to redirect to a cutom page on a (example database) error, and display the message, when using passport-local. here's the code:

passport.use(new LocalStrategy({ 
  passReqToCallback: true 
  }, function( req, username, password, done ) {
    done({error:'mycustomerrormessage'});
  }
));

the routing looks like:

app.post('/auth/local', passport.authenticate('local', { 
    successRedirect: '/', 
    failureRedirect: '/', 
    failureFlash: true 
}));

when the error occurs, the url stay /auth/local, with a nasty [object Object] content.

if I call

done( null, false, { message: "error message"})

than passport redirects to /, and I can flash the message, but how can I set a redirection in case I call the verify function with a first not null parameter and do something with that error?

based on express documentation, you can configure error handling middleware as following:

app.use(function(err, req, res, next){
  console.error(err.stack);
  res.send(500, 'Something broke!');
});

The four parameter signature indicates that this is an error handling definition.

See http://expressjs.com/guide.html#error-handling