Devise\Users\UserManager::updateRules PHP Method

    public function updateRules($id, $input)
    {
        $updateRules = array('email' => "required|email|unique:users,email,{$id}", 'username' => "required|unique:users,username,{$id}", 'group_id' => 'required|exists:groups,id');
        $password = array_get($input, 'password', null);
        if ($password) {
            $updateRules['password'] = 'required|min:6';
            $updateRules['password_confirmation'] = 'required|min:6|same:password';
        }
        return $updateRules;
    }