Implements hook_language_delete().
function locale_language_delete($language) {
// Remove translations.
Drupal::service('locale.storage')
->deleteTranslations(array(
'language' => $language->langcode,
));
// Remove interface translation files.
module_load_include('inc', 'locale', 'locale.bulk');
locale_translate_delete_translation_files(array(), array(
$language->langcode,
));
// Remove translated configuration objects.
\Drupal\locale\Locale::config()
->deleteLanguageTranslations($language->langcode);
// Changing the language settings impacts the interface:
_locale_invalidate_js($language->langcode);
cache('page')
->deleteAll();
// Clear locale translation caches.
locale_translation_status_delete_languages(array(
$language->langcode,
));
cache()
->delete('locale:' . $language->langcode);
}