protected function setError($errorStatus)
    {
        # error status
        if (! is_int($errorStatus)
            || 0 > $errorStatus
            || 8 < $errorStatus
        )
            throw new \InvalidArgumentException(
                'Invalid error status for UploadedFile; must be an UPLOAD_ERR_* constant'
            );

        $this->error = $errorStatus;
        return $this;
    }