protected function findPackageKey($package_name)
    {
        $package_key = null;
        // In most cases the package name is already used as the array key.
        if (isset(static::$packageToCleanup[$package_name])) {
            $package_key = $package_name;
        } else {
            // Handle any mismatch in case between the package name and array key.
            // For example, the array key 'mikey179/vfsStream' needs to be found
            // when composer returns a package name of 'mikey179/vfsstream'.
            foreach (static::$packageToCleanup as $key => $dirs) {
                if (strtolower($key) === $package_name) {
                    $package_key = $key;
                    break;
                }
            }
        }
        return $package_key;
    }