Allow deletion of a setting from overridden settings
|Reported by:||claudep||Owned by:||nobody|
|Cc:||Triage Stage:||Ready for checkin|
|Has patch:||yes||Needs documentation:||no|
|Needs tests:||no||Patch needs improvement:||no|
Currently, if you call del settings.SOME_SETTING when the settings have been customized with override_settings, the setting still exists if it was pre-existing in the original settings object. See #17966 for a real use case.