public function runDrushCommand($drush_command, $alias = NULL) {

        if ($alias == NULL) {
            $alias = $this->getDrushAlias();
        }

        $cmd = "drush {$alias} $drush_command";

        $process = new Process($cmd);
        $process->setTimeout(null);
        $process->run();
        return trim($process->getOutput());
    }