[ANN] mpi4py release 3.1.2

[Lisandro Dalcin]

**WARNING**: This is the last release supporting Python 2.

* `mpi4py.futures`: Add `_max_workers` property to `MPIPoolExecutor`.

* `mpi4py.util.dtlib`: Fix computation of alignment for predefined datatypes.

* `mpi4py.util.pkl5`: Fix deadlock when using ``ssend()`` + ``mprobe()``.

* `mpi4py.util.pkl5`: Add environment variable `MPI4PY_PICKLE_THRESHOLD`.

* `mpi4py.rc`: Interpret ``"y"`` and ``"n"`` strings as boolean values.

* Fix/add typemap/typestr for `MPI.WCHAR`/`MPI.COUNT` datatypes.

* Minor fixes and additions to documentation.

* Minor fixes to typing support.

* Support for local version identifier (PEP-440).

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Lisandro Dalcin
============
Senior Research Scientist
Extreme Computing Research Center (ECRC)
King Abdullah University of Science and Technology (KAUST)
http://ecrc.kaust.edu.sa/