Currently, private names such as '__location' will get both name mangled and converted into an attribute, while `__location_` will get mangled, but not converted as the final name is sundered (e.g. `_MyEnum__location_`).

Just in case anyone is actually using private name Enum members we'll deprecate in 3.10, and in 3.11 private names will:

- not be converted
- not raise sunder errors