Pyrsistent

* Add universal wheels for MacOS, thanks ntamas for this!
* Add support for Python 3.10, thanks hugovk for this!
* Fix 236 compilation errors under Python 3.10.
* Drop official support for Python 3.6 since it's EOL since 2021-12-23.
* Fix 238, failing doc tests on Python 3.11, thanks musicinmybrain for this!

* Fix 209 Update freeze recurse into pyrsistent data structures and thaw to recurse into lists and dicts,
Thanks phil-arh for this!
NB! This is a backwards incompatible change! To keep the old behaviour pass `strict=False` to freeze and thaw.
* Fix 226, stop using deprecated exception.message. Thanks hexagonrecursion for this!
* Fix 211, add union operator to persistent maps. Thanks bowbahdoe for this!
* Fix 194, declare build dependencies through pyproject.toml. Thanks jaraco for this!
* Officially drop Python 3.5 support.
* Fix 223, release wheels for all major platforms. Thanks johnthagen for helping out with this!
* Fix 221, KeyError obscured by TypeError if key is a tuple. Thanks ganwell for this!
* Fix LICENSE file name spelling. Thanks ndowens and barentsen for this!
* Fix 216, add abstractmethod decorator for CheckedType and ABCMeta for _CheckedTypeMeta. Thanks ss18 for this!
* Fix 228, rename example classes in tests to avoid name clashes with pytest.

* Fix 208, release v0.17.3 with proper meta data requiring Python >= 3.5.

* Restrict package to Python >= 3.5 to not break unpinned Python 2 dependencies. Thanks vphilippon
for this!

0.17.0 (yanked for Python 2 compatibility), 2020-09-08
* Remove Python 2 support code. This includes dropping some compatibility code and the dependency on
six. Thanks djailla for this.
* Fix 200, python 3 exception chaining. This is a minor backwards incompatibility, hence stepping
to 0.17.0. Thanks cool-RR for this!

* Add "python_requires >= 2.7" to setup.py in preparation for Python 2.7 incompatible updates
in 0.17. This is the last version of pyrsistent that can be used with Python 2.7.

0.17.2 (yanked awaiting proper fix for Python 3 req), 2020-09-09
* Same as 0.17.1 released with more recent version of setuptools to get proper meta data for in place.

* No major updates but Python 2 support no longer guaranteed.
* Fix 192, 'ignore_extra' for 'pvector_field'. Thanks ss18 for this!
* Fix 191, include LICENCE in distribution. Thanks johnthagen for this!
* Fix 190, minor MyPy errors. Thanks Qhesz for this!