private function setXliffDirectory(InputInterface $input, OutputInterface $output)
    {
        $this->txlang = $input->getOption('xliff');

        if ($this->txlang === null) {
            $this->txlang = $this->getTransifexConfigValue('/languages_tx');

            if ($this->txlang === null) {
                throw new \RuntimeException('Error: unable to determine transifex root folder.');
            }
            $this->writelnVerbose($output, sprintf('<info>automatically using xliff folder: %s</info>', $this->txlang));
        }
    }