from abc import ABCMeta, abstractmethod
from types import new_class

class MyABC(metaclass=ABCMeta):
	@abstractmethod
	def m(self): ...

def m(self): ...

namespace = dict(m=m)

C = type("C", (MyABC,), namespace)

C().m()  # no error

# C = new_class("C", (MyABC,), namespace)

C().m()  # error

# ABCMeta.__prepare__ seems to be lopping off the `m` argument:
assert ABCMeta.__prepare__("C", (MyABC,), namespace) # error; should contain `m`