DrushCommand.php

<?php
/**
 * @file
 * Contains \Drupal\AppConsole\Command\DrushCommand.
 */

namespace Drupal\AppConsole\Command;

use Symfony\Component\Console\Input\InputArgument;
use Symfony\Component\Console\Input\InputInterface;
use Symfony\Component\Console\Output\OutputInterface;

class DrushCommand extends ContainerAwareCommand
{
    /**
     * {@inheritdoc}
     */
    protected function configure()
    {
        $this
          ->setName('drush')
          ->setDescription($this->trans('commands.drush.description'))
          ->addArgument('args', InputArgument::IS_ARRAY, $this->trans('commands.drush.arguments.args'))
          ->setHelp($this->trans('commands.drush.help'));
    }

    /**
     * {@inheritdoc}
     */
    protected function execute(InputInterface $input, OutputInterface $output)
    {
        $args = '';
        if ($arguments = $input->getArgument('args')) {
            $args .= ' ' . implode(' ', $arguments);
            $c_args = preg_replace('/[^a-z0-9-= ]/i', '', $args);
        }

        if (`which drush`) {
            system('drush' . $c_args);
        } else {
            $output->write("<error>" . $this->trans('commands.drush.message.not_found') . "</error>");
        }
    }
}