code: public function bootstrap($app)
      {
          $app->i18n->translations['devgroup.events-system'] = [
              'class' => 'yii\i18n\PhpMessageSource',
              'sourceLanguage' => 'en-US',
              'basePath' => '@DevGroup/EventsSystem/messages',
          ];
          $error = [];
          try {
              foreach (EventHelper::getActiveHandlersList() as $handler) {
                  Event::on($handler['class'], $handler['name'], $handler['callable'], $handler['data']);
              }
          } catch (\yii\db\Exception $e) {
              $error = [
                  'message' => '`DevGroup\EventsSystem` extension is not fully installed yet.',
                  'hint' => 'Please run the `./yii migrate --migrationPath=@DevGroup/EventsSystem/migrations` command from your application directory to finish the installation process.',
              ];
          } catch (\Exception $e) {
              $error = [
                  'message' => $e->getCode(),
                  'hint' => $e->getMessage(),
              ];
          }
          if (empty($error) === false) {
              if ($app instanceof \yii\console\Application) {
                  $app->on(Application::EVENT_BEFORE_ACTION, function ($event) use ($app, $error) {
                      $app->controller->stdout(PHP_EOL . str_repeat('=', 80) . PHP_EOL . PHP_EOL);
                      $app->controller->stderr($error['message'] . PHP_EOL);
                      $app->controller->stdout($error['hint'] . PHP_EOL);
                      $app->controller->stdout(PHP_EOL . str_repeat('=', 80) . PHP_EOL);
                  });
              } elseif ($app instanceof \yii\web\Application && YII_DEBUG === true) {
                  $app->session->setFlash(
                      'warning',
                      Html::tag('h4', $error['message']) . Html::tag('p', $error['hint'])
                  );
              }
          }
      }
docs: Bootstrap method to be called during application bootstrap stage.
  @param \yii\base\Application $app the application currently running