public function exec($command)
    {
        $this->debug("Executing: $command");
        $output = $returnValue = null;
        exec($command, $output, $returnValue);

        if ($returnValue != 0) {
            throw new \RuntimeException('Error executing command: '
                . $command . ' : ' . implode("\n", $output));
        }

        return implode("\n", $output);
    }