side_effect mocked method lose reference to instance

[Adnan Umer]

When a method/bounded function is mocked and side_effect is supplied to it, the side_effect function doesn't get the reference to the instance.

Suppose we have something like this

class SomeClass:
    def do_something(self, x):
        pass

def some_function(x):
    cls = SomeClass()
    y = class.do_something(x)
    return y

And the test for some_function will be

def do_something_side_effect(x):
    retrun x

def test_some_function():
    with mock.path("SomeCass.do_something") as do_something_mock:
        do_something_mock.side_effect = do_something_side_effect
        assert some_function(1)

Here do_something_side_effect mock will not have access to SomeClass instance.

[Chris Withers]

This repo is only for issues that are specific to the backport.
Please report issues with mock in the upstream bug tracker at https://bugs.python.org/.
Once issues are fixed upstream, they can be backported here.