Deprecating classes with subclasses

[tommy-waltmann]

Deprecation decorator doesn't work on classes if the class being deprecated has a subclass that inherits from it, even if all the subclasses are marked deprecated as well.

[briancurtin]

Hey, thanks for the report! That's not something I've come across in the past and don't have a fix off the top of my head. If you happen to beat me to it I'd be happy to review a PR.

[bdice]

I worked a bit with @tommy-waltmann on this problem. From my understanding, decorators and classes don't play nicely together when it comes to inheritance. This StackOverflow post seems related: https://stackoverflow.com/questions/2542747/class-decorators-inheritance-super-and-maximum-recursion