private function addExtension($name, $prettyVersion)
    {
        $extraDescription = null;

        try {
            $version = $this->versionParser->normalize($prettyVersion);
        } catch (\UnexpectedValueException $e) {
            $extraDescription = ' (actual version: '.$prettyVersion.')';
            if (preg_match('{^(\d+\.\d+\.\d+(?:\.\d+)?)}', $prettyVersion, $match)) {
                $prettyVersion = $match[1];
            } else {
                $prettyVersion = '0';
            }
            $version = $this->versionParser->normalize($prettyVersion);
        }

        $packageName = $this->buildPackageName($name);
        $ext = new CompletePackage($packageName, $version, $prettyVersion);
        $ext->setDescription('The '.$name.' PHP extension'.$extraDescription);
        $this->addPackage($ext);
    }