public function __construct()
 {
     parent::__construct('invalid_client', 'Client authentication failed.');
     $this->addHeader('www-authenticate', 'Basic realm="OAuth2"');
 }
 public function __construct()
 {
     parent::__construct('unauthorized_client_for_grant_type', 'The client is unauthorized for the grant type.');
 }
 public function __construct()
 {
     parent::__construct('unauthorized_scope', 'Scope not allowed.');
 }
 public function __construct($errorMessage = 'Invalid access token.')
 {
     parent::__construct('invalid_access_token', $errorMessage);
 }
 public function __construct()
 {
     parent::__construct('invalid_request_user_credentials_not_found', 'The user credentials are required.');
 }
 public function __construct()
 {
     parent::__construct('invalid_grant', 'User authentication failed.');
 }
 public function __construct($errorMessage = null)
 {
     parent::__construct('invalid_request_access_token_not_found', 'The access token is required.');
 }