/**
 * Implements hook_ajax_render_alter().
 */
function {{ machine_name }}_ajax_render_alter(array &$data) {
  // Inject any new status messages into the content area.
  $status_messages = ['#type' => 'status_messages'];
  $command = new \Drupal\Core\Ajax\PrependCommand('#block-system-main .content', \Drupal::service('renderer')->renderRoot($status_messages));
  $data[] = $command->render();
}