Calling instance method from class method, allowed in python3, disallowed in python 2?

The following code snippet gives error in python2 but no error with python3

class Steps(object):
    def step(self, msg="Default"):
        if not hasattr(self, "funky_attr"):
            print('No attr')
        print(self)
        print(msg)

class FirstTest(Steps):
    @classmethod
    def test_setup(cls):
      cls.step("This is the message")

if __name__ == '__main__':
    C = FirstTest()
    C.test_setup()

With python 2 it produces the error:

TypeError: unbound method step() must be called with CifsTest instance as first argument (got str instance instead)

While with python 3 it runs fine:

No attr

This is the message # Note here the 'self' is the str

Default

Is this the correct behavior ?

Python3 allows calling instance method from class methods ?