/**
  * Schedules a config handlers file to be loaded.
  * 
  * @param      string The path to a config_handlers.xml file.
  * 
  * @author     Dominik del Bondio <*****@*****.**>
  * @since      1.0.0
  */
 public static function addConfigHandlersFile($filename)
 {
     if (!isset(self::$handlerFiles[$filename])) {
         if (!is_readable($filename)) {
             throw new AgaviUnreadableException('Configuration file "' . $filename . '" does not exist or is unreadable.');
         }
         self::$handlerFiles[$filename] = false;
         self::$handlersDirty = true;
     }
 }