public static function clearNAVCache(PonyDocsProductVersion $version)
 {
     error_log("INFO [" . __METHOD__ . "] Deleting cache entry of NAV for product " . $version->getProductName() . " version " . $version->getVersionName());
     $cache = PonyDocsCache::getInstance();
     $key = "NAVDATA-" . $version->getProductName() . "-" . $version->getVersionName();
     $cache->remove($key);
 }