protected function buildServerBundle($langCode)
    {
        $extensions = common_ext_ExtensionsManager::singleton()->getInstalledExtensions();
        $extensions = helpers_ExtensionHelper::sortByDependencies($extensions);
        $translations = [];
        foreach ($extensions as $extension) {
            $file = $extension->getDir(). 'locales' . DIRECTORY_SEPARATOR . $langCode. DIRECTORY_SEPARATOR . 'messages.po';
            $new = l10n::getPoFile($file);
            if (is_array($new)) {
                $translations = array_merge($translations, $new);
            }
        }
        $cache = $this->getServiceLocator()->get(common_cache_Cache::SERVICE_ID);
        $cache->put($translations, self::TRANSLATION_PREFIX.$langCode);
        return $translations;
    }