Should we remove abstract-method?

[mbyrnepr2]

Current problem

abstract-method documentation.

The documentation states that this message is emitted when an abstract method (i.e. raise NotImplementedError) is not overridden in concrete class.

A concrete class is one where all the abstract methods have been implemented.

The problem with abstract-method is that we don't know for sure if a class is intended to be a concrete class or not. The only way we would know for sure is if it does contain all of the implemented abstract methods - but by that point the check is not useful.

The following scenario (modified from one of the examples in the documentation) is valid Python but it would emit abstract-method:

class Pet:
    def make_sound(self):
        raise NotImplementedError


class Cat(
    Pet
):  #  W0223: Method 'make_sound' is abstract in class 'Pet' but is not overridden in child class 'Cat' (abstract-method)
    def jump_up(self):
        print("jump!")


class Tiger(Cat):
    """This is the concrete class"""
    def make_sound(self):
        print("rrr!")


Tiger().make_sound()
Tiger().jump_up()

The other example from the documentation emits abstract-method; however the base class does not inherit from abc.ABC, so this example emits a warning even though the class, which is not implementing the abstract method, instantiates without error:

import abc


class WildAnimal:
    @abc.abstractmethod
    def make_sound(self):
        pass


class Panther(WildAnimal):  # [abstract-method]
    pass


Panther().make_sound()

Desired solution

Deprecate and remove abstract-method.

Additional context

#9979
#7950
#3098

Related message https://pylint.readthedocs.io/en/latest/user_guide/messages/error/abstract-class-instantiated.html