class Broken

class Broken extends PluginBase implements BlockPluginInterface, ContainerFactoryPluginInterface {
    use BlockPluginTrait;
    use CacheableDependencyTrait;
    
    /**
     * The current user.
     *
     * @var \Drupal\Core\Session\AccountInterface
     */
    protected $currentUser;
    
    /**
     * Creates a Broken Block instance.
     *
     * @param array $configuration
     *   A configuration array containing information about the plugin instance.
     * @param string $plugin_id
     *   The plugin ID for the plugin instance.
     * @param mixed $plugin_definition
     *   The plugin implementation definition.
     * @param \Drupal\Core\Session\AccountInterface $current_user
     *   The current user.
     */
    public function __construct(array $configuration, $plugin_id, $plugin_definition, AccountInterface $current_user) {
        parent::__construct($configuration, $plugin_id, $plugin_definition);
        $this->currentUser = $current_user;
    }
    
    /**
     * {@inheritdoc}
     */
    public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
        return new static($configuration, $plugin_id, $plugin_definition, $container->get('current_user'));
    }
    
    /**
     * {@inheritdoc}
     */
    public function build() {
        $build = [];
        if ($this->currentUser
            ->hasPermission('administer blocks')) {
            $build += $this->brokenMessage();
        }
        return $build;
    }
    
    /**
     * {@inheritdoc}
     */
    public function blockForm($form, FormStateInterface $form_state) {
        return $this->brokenMessage();
    }
    
    /**
     * Generate message with debugging information as to why the block is broken.
     *
     * @return array
     *   Render array containing debug information.
     */
    protected function brokenMessage() {
        $build['message'] = [
            '#markup' => $this->t('This block is broken or missing. You may be missing content or you might need to enable the original module.'),
        ];
        return $build;
    }

}