DbUpdateController::requirements

public DbUpdateController::requirements($severity, array $requirements, Request $request)

public function requirements($severity, array $requirements, Request $request) {
  $options = $severity == REQUIREMENT_WARNING ? array('continue' => 1) : array();
  // @todo Revisit once https://www.drupal.org/node/2548095 is in. Something
  // like Url::fromRoute('system.db_update')->setOptions() should then be
  // possible.
  $try_again_url = Url::fromUri($request->getUriForPath(''))->setOptions(['query' => $options])->toString(TRUE)->getGeneratedUrl();

  $build['status_report'] = array(
    '#theme' => 'status_report',
    '#requirements' => $requirements,
    '#suffix' => $this->t('Check the messages and <a href=":url">try again</a>.', array(':url' => $try_again_url))
  );

  $build['#title'] = $this->t('Requirements problem');
  return $build;
}