update_check_requirements example

public function handle($op, Request $request) {
    require_once $this->root . '/core/includes/install.inc';
    require_once $this->root . '/core/includes/update.inc';

    drupal_load_updates();

    if ($request->query->get('continue')) {
      $request->getSession()->set('update_ignore_warnings', TRUE);
    }

    $regions = [];
    $requirements = update_check_requirements();
    $severity = drupal_requirements_severity($requirements);
    if ($severity == REQUIREMENT_ERROR || ($severity == REQUIREMENT_WARNING && !$request->getSession()->has('update_ignore_warnings'))) {
      $regions['sidebar_first'] = $this->updateTasksList('requirements');
      $output = $this->requirements($severity, $requirements, $request);
    }
    else {
      switch ($op) {
        case 'selection':
          $regions['sidebar_first'] = $this->updateTasksList('selection');
          $output = $this->selection($request);
          break;