Pycharm warning: must implement all abstract methods

Question

Code

class A(object):
    def a(self):
        raise NotImplementedError

class B(A):
    def a(self):
        return 7

class C(B):
    pass

Why does Pycharm complain?

Problem synopsis      Class C must implement all abstract methods

Answer 1

It's a reported bug - you can vote for it here: https://youtrack.jetbrains.com/issue/PY-16132