private function processEnvironmentReaderPass(ContainerBuilder $container)
    {
        // Register Behat context readers.
        $references = $this->processor->findAndSortTaggedServices($container, ContextExtension::READER_TAG);
        $definition = $container->getDefinition('drupal.context.environment.reader');

        foreach ($references as $reference) {
            $definition->addMethodCall('registerContextReader', array($reference));
        }
    }