various updates from upstream python/typing repo:

- Added typing.Counter and typing.ChainMap generics
- More flexible typing.NamedTuple
- Improved generic ABC caching
- More tests
- Bugfixes
- Other updates

* Add Misc/NEWS entry

* Add issue number

(cherry picked from commit b692dc8)

 various updates from upstream python/typing repo:

- Added typing.Counter and typing.ChainMap generics
- More flexible typing.NamedTuple
- Improved generic ABC caching
- More tests
- Bugfixes
- Other updates

* Add Misc/NEWS entry

* Add issue number

(cherry picked from commit b692dc8)

various updates from upstream python/typing repo:

- Added typing.Counter and typing.ChainMap generics
- More flexible typing.NamedTuple
- Improved generic ABC caching
- More tests
- Bugfixes
- Other updates

* Add Misc/NEWS entry

* Add issue number

Contributed by Ivan Levkivskyi @ilevkivskyi

(cherry picked from commit b692dc8)

various updates from upstream python/typing repo:

- Added typing.Counter and typing.ChainMap generics
- More flexible typing.NamedTuple
- Improved generic ABC caching
- More tests
- Bugfixes
- Other updates
* Add Misc/NEWS entry


(cherry picked from commit b692dc8)

- Ensure travis job has kicked off before checking for `pending` status.

Closes python#28

* Use `extend-ignore` in flake8 config

This option allows to add extra ignored rules to the default list
instead of replacing it.

The default exclusions are: E121, E123, E126, E226, E24, E704,
W503 and W504.

Fixes python#28.

Refs:
* https://github.com/pypa/setuptools/pull/2486/files#r541943356
* https://flake8.pycqa.org/en/latest/user/options.html#cmdoption-flake8-extend-ignore
*
https://flake8.pycqa.org/en/latest/user/options.html#cmdoption-flake8-ignore

* Enable complexity limit. Fixes jaraco/skeleton#34.

* Replace pep517.build with build (python#37)

* Replace pep517.build with build

Resolves python#30

* Prefer simple usage

Co-authored-by: Jason R. Coombs <[email protected]>

* Use license_files instead of license_file in meta (python#35)

Singular `license_file` is deprecated since wheel v0.32.0.

Refs:
* https://wheel.readthedocs.io/en/stable/news.html
* https://wheel.readthedocs.io/en/stable/user_guide.html#including-license-files-in-the-generated-wheel-file

Co-authored-by: Jason R. Coombs <[email protected]>

28: test clean final r=ltratt a=nanjekyejoannah

This PR does the final cleanups to address the following:
- Allow higher recursion limit for some tests
- skip some tests that require very high recursion limits, I used the allowed limit by convention for the first item above
- call reset to allow warning propagation in some tests

Note:

Existing py3k tests fail with a segfault with -3 flag if not run individually, deleting this context manager in over 300 files will take forever, lets only run `test_py3kwarn` and the rest should be tested locally if modified. 

It took me long to know the source of this segfault, I have solved any issues with new context manager I introduce.

If this PR is merged, we can modify the CI, I am going back to implementing the warnings now.

Co-authored-by: Joannah Nanjekye <[email protected]>