Prevent access to untranslated pages with Drupal 8
It is not uncommon when a multilingual Drupal 8 project is implemented, that the pages translations are not ready at the time of production. If making a Drupal 8 multilingual site has become really easy to implement, there is now a fundamental difference with Drupal 7: it is impossible to disable a language. Either install a language, or delete it. This change is assumed, and voluntary, so as to not generate unnecessary complexity for questionable gain.