Release 0.760 planning

[JukkaL]

I plan to release mypy 0.760 next Tue (Dec 17) and cut the release branch for 0.760 this Thu (Dec 12).

Please add comments to this issue if you have any PR you'd like to be included. Ideally those PRs should be landed before the release branch is cut, to minimize cherry-picking.

[TH3CHARLie]

Two minor fix PR purposed by myself #8066 and #8107, I think both of them are ready to be review with easy efforts and merge quickly.

[msullivan]

I would like #8134 to make it in (not so much because I care if it is in the release itself, but I don't want to wait until after our testing period to deploy it internally)

[JukkaL]

I created the release branch. #8066, #8107 and #8134 were included.

[JukkaL]

Mypy 0.760 is out: https://mypy-lang.blogspot.com/2019/12/mypy-0760-released.html

[JukkaL]

I uploaded 0.761 which has no functionality changes but includes the source tarball which was missing from 0.760.