public function getSchemaErrorMessage()
    {
        $message = NULL;

        foreach ($this->lastSchemaErrors as $error) {
            $message .= sprintf(
                "[%s] %s\n", $error['property'], $error['message']
            );
        }

        if (!empty($message)) {
            $message = self::FAIL_JSON_SCHEMA_MESSAGE . $message;
        }

        return $message;
    }