public static function changeFilePermissions($filename, $mode = 0644)
    {

        // make the passed filename OS compliant
        $toBeChanged = Setup::prepareOsSpecificPath($filename);

        // change the mode, if we're not on Windows
        if (SetupKeys::OS_FAMILY_WINDOWS !== strtolower(php_uname('s'))) {
            chmod($toBeChanged, $mode);
        }
    }