public function __construct($target)
 {
     $message = 'Target location should be registered: ' . $target;
     parent::__construct($message, 3);
 }
 public function __construct($location)
 {
     $message = 'No such location registered: ' . $location;
     parent::__construct($message, 1);
 }
 public function __construct($location)
 {
     $message = 'Location already registered: ' . $location;
     parent::__construct($message, 2);
 }