How can I access error object of SequelizeJS (NodeJS)

I have written following piece of code using 'sequelizeJS' and want to access error object to extract the validation message contained by the err object.

var userData = {name: "waqas", email: null};

db.User
  .create(userData)
  .success(function(user) {
    console.log(user);
  })
  .error(function(err){
    console.log(err);  // want to get validation message from 'err' object

  });

The output of console.log(err) is:

{ [Error: ER_BAD_NULL_ERROR: Column 'email' cannot be null]
  code: 'ER_BAD_NULL_ERROR',
  errno: 1048,
  sqlState: '23000',
  index: 0,
  sql: 'INSERT INTO `users` (`id`,`name`,`email`,`platform`,`email_flag`,`purchased_balance`,`subscription_balance`,`created_at`,`updated_at`) VALUES (DEFAULT,\'waqas\',NULL,\'ios\',true,0,0,\'2014-08-17 06:09:08\',\'2014-08-17 06:09:08\');' }