Adldap\Auth\Guard::validateCredentials PHP Method

    protected function validateCredentials($username, $password)
    {
        if (empty($username)) {
            // Check for an empty username.
            throw new UsernameRequiredException('A username must be specified.');
        }
        if (empty($password)) {
            // Check for an empty password.
            throw new PasswordRequiredException('A password must be specified.');
        }
    }