python: abstract base class' __init__(): initializion or validation?

class ABC is an "abstract base class". class X is its subclass.

There's some work that needs to be done in any subclass of ABC, which is easy to forget or do incorrectly. I'd like ABC.__init__() to help catch such mistakes by either:

(1) starting that work, or (2) validating it

This impacts whether super().__init__() is called at the start or at the end of X.__init__().

Here's a simplified example for illustration purposes:

Suppose every subclass of ABC must have an attribute registry, and it must be a list. ABC.__init__() can either (1) initialize registry or (2) check that it was properly created. Following is the sample code for each approach.

Approach 1: initialize in ABC

class ABC:
    def __init__(self):
        self.registry = []

class X:
    def __init__(self):
        super().__init__()
        # populate self.registry here
        ...

Approach 2: validate in ABC

class ABC:
    class InitializationFailure(Exception):
        pass
    def __init__(self):
        try:
            if not isinstance(self.registry, list):
                raise ABC.InitializationError()
        except AttributeError:
            raise ABC.InitializationError()

class X:
    def __init__(self):
        self.registry = []
        # populate self.registry here
        ...
        super().__init__()

Which is a better design?