Issue #3231996: Ensure file system is writeable

src/Validator/WritableFileSystemValidator.php

@@ -35,6 +35,11 @@ class WritableFileSystemValidator implements EventSubscriberInterface {
    *
    * @param \Drupal\automatic_updates\Event\UpdateEvent $event
    *   The event object.
+   *
+   * @todo It might make sense to use a more sophisticated method of testing
+   *   writability than is_writable(), since it's not clear if that can return
+   *   false negatives/positives due to things like SELinux, exotic file
+   *   systems, and so forth.
    */
   public function checkPermissions(UpdateEvent $event): void {
     $messages = [];