public function getInstallPath(PackageInterface $package)
    {
        $textpattern = new Textpattern();
        $path = $textpattern->getRelativePath();
        $themes = $path . '/admin-themes';

        // Textpattern <= 4.5.x uses 'theme' directory.
        if (!file_exists($themes)) {
            $themes = $path . '/theme';
        }

        return $themes . '/' . basename($package->getPrettyName());
    }