private function cleanInstalledPaths()
    {
        $changes = false;
        foreach ($this->installedPaths as $key => $path) {
            // This might be a relative path as well
            $alternativePath = realpath($this->getPHPCodeSnifferInstallPath() . DIRECTORY_SEPARATOR . $path);

            if ((is_dir($path) === false || is_readable($path) === false) &&
                (is_dir($alternativePath) === false || is_readable($alternativePath) === false)
            ) {
                unset($this->installedPaths[$key]);
                $changes = true;
            }
        }
        return $changes;
    }