Good catch Serhiy - I'd completely missed that in the original review, and definitely agree we should make that fix independently of the exception chaining idea.

While that correction will fix the specific __getattr__ example given, we still have the problem of actual errors in looking up __set_name__ on the class (e.g. in a metaclass or in __getattribute__) and errors when calling it being hard to debug, as the traceback will point to the class header without giving the name of the offending attribute.