public function helperExec($cmd)
    {
        if ($this->resolve('EXPLAIN')) {
            $this->output->writeln("# Task needs the following helper command:");
            $this->output->writeln("# " . str_replace("\n", "\\n", $cmd));
        }
        $ret = '';
        $this->executor->execute($cmd, $ret);
        return $ret;
    }