[3.7] bpo-17185: Add __signature__ to mock that can be used by inspect for signature (GH11048) by miss-islington · Pull Request #11125 · python/cpython

@tirkarthi @miss-islington

…signature (GH11048)

* Fix partial and partial method signatures in mock

* Add more calls

* Add NEWS entry

* Use assertEquals and fix markup in NEWS

* Refactor branching and add markup reference for functools

* Revert partial object related changes and fix pr comments
(cherry picked from commit f7fa62e)

Co-authored-by: Xtreak <tirkarthi@users.noreply.github.com>