CI: Unpin pytest
- [ ] closes #35261

have made a start working through the failures. we should be able to get mypy to green here and then when pytest 6.0.0 is released the upstream fixes should cause ci to go red since we have `warn_unused_ignores = True` in setup.cfg.
cc @bluetech @asottile  Hello @simonjayhawkins! Thanks for updating this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:







There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers: 

##### Comment last updated at 2020-07-29 14:30:49 UTC Nice work. Are you planning to drop some of the type ignores on the next RC? I see some of the upstream issues you've opened have been closed > Nice work. Are you planning to drop some of the type ignores on the next RC? I see some of the upstream issues you've opened have been closed

we could release the pin on `CI / Checks` only with this PR and get immediate benefit from the type checking. or happy to wait for the upstream fixes and reduce the diff here. (the type:ignores for the fixed issues will give mypy errors since we have `warn_unused_ignores = True` in the config)

@bluetech has added tests for the fixed issues so shouldn't be an issue, but could also change the `CI /Checks` environment here to use pytest master to make sure.


 > I see some of the upstream issues you've opened have been closed

There are basically three issues. two are fixed. I still need to look into the other. https://github.com/pytest-dev/pytest/issues/7495 @TomAugspurger I've labelled this 1.2 for now. Is there a benefit to unpinning on 1.1.x? test failures unrelated. The ci environments are resolving to pytest 6.0.0 in Linux py37_locale and Windows py36_np15 on azure, CI / Checks on GitHub actions so I think this is good to go. @TomAugspurger  Actually, I'm second-guessing not backporting this. I think we'll want a consistent pytest version for both branches being actively developed. What do you think? > Actually, I'm second-guessing not backporting this. I think we'll want a consistent pytest version for both branches being actively developed. What do you think?

sure. happy to backport. should be a benefit to users of 1.1.1 onwards (will be interesting to see if we get any issues on 1.1.0 regarding the pin, now that pytest 6.0.0 is released.) Great, thanks. @MeeseeksDev backport to 1.1.x