Issue #3231996: Ensure file system is writeable

tests/modules/automatic_updates_test_disable_validators/src/AutomaticUpdatesTestDisableValidatorsServiceProvider.php

@@ -8,6 +8,10 @@ use Drupal\Core\Site\Settings;
 
 /**
  * Allows specific validators to be disabled by site settings.
+ *
+ * This should only really be used by functional tests. Kernel tests should
+ * override their ::register() method to remove service definitions; build tests
+ * should stay out of the API/services layer unless absolutely necessary.
  */
 class AutomaticUpdatesTestDisableValidatorsServiceProvider extends ServiceProviderBase {