Implements hook_language_delete().
function locale_language_delete($language) {
// Remove translations.
locale_storage()
->deleteTranslations(array(
'language' => $language->langcode,
));
// Remove interface translation files.
module_load_include('inc', 'locale', 'locale.bulk');
locale_translate_delete_translation_files($language->langcode);
_locale_invalidate_js($language->langcode);
// Changing the language settings impacts the interface:
cache('page')
->deleteAll();
// Clearing all locale cache from database
cache()
->delete('locale:' . $language->langcode);
}