try-except and abc https://bugs.python.org/issue12029

issue12029.py

>>> Error(abc.ABC, Exception): pass
...
>>> EndOfTheWorld(Exception): pass
...
>>> Error.register(EndOfTheWorld)
<class '__main__.EndOfTheWorld'>
>>> e = EndOfTheWorld()
>>> isintance(e, Error)
True
>>> try:
...     raise e
... except Error:
...     pass
...
Traceback (most recent call last):
  File "<stdin>", line 2, in <module>
__main__.EndOfTheWorld