The route "foobar_by_name" does not exist. (using sfRouting in a task)

Question

I have created a custom task in symfony (1.3.6), running on Ubuntu 10.0.4.

I am generating urls in the task. This is a snippet of some of my code:

// In the custom task (lib/task/mySomethingSomethingTask.php)

  protected function execute($arguments = array(), $options = array())
  {
    //create a context
    $app = sfProjectConfiguration::getApplicationConfiguration('frontend', 'prod', true);
    sfContext::createInstance($app);
    sfContext::getInstance()->getConfiguration()->loadHelpers(array('Url', 'Asset', 'Tag'));
    $routing = $this->getProductionRouting();

    // initialize the database connection
    $databaseManager = new sfDatabaseManager($this->configuration);
    $connection = $databaseManager->getDatabase($options['connection'])->getConnection();

    // add your code here
    // ...
  }

/**
   * Gets routing with the host url set to the url of the production server
   * @return sfPatternRouting
   */
  protected function getProductionRouting()
  {
    $routing = $this->getRouting();
    $routingOptions = $routing->getOptions();
    $routingOptions['context']['host'] = sfConfig::get('app_server_name', 'www.example.com');
    $routing->initialize($this->dispatcher, $routing->getCache(), $routingOptions);
    return $routing;
  }

// My frontend/config/routing.yml

foobar_by_name:
  url:   /foo/bar/:name/someguy.html
  param: { module: something, action: somethingDarkSide }


// In the model layer (the method called by the task)

   public static function getSomeData(sfRouting $routing)
   {
        $name = 'family-guy'
        $parameters = array('name'=>$name);
        $url = $routing->generate('foobar_by_name', $parameters, true);   // <- ERROR !
   }

When the method getSomeData() is called in the task, I get the error message:

The route "foobar_by_name" does not exist.

Does anyone know how to resolve this?