This branch is for development towards getting the python bindings working under
Python 3. [0]

Branch type: dev branch off trunk.

The upstream Python project has previously announced End of Life for Python 2,
with no updates passed some point in 2020. So the bindings need to be updated to
support Python 3. In order to not have to maintain different code for the
difference versions, the py3c [1] was chosen to provide standard compatibility
features for the C extension interfaces for each version.

TODO
----

* Windows build has been updated to work with the py3c library for python swig
  bindings:
    * Python 2 compiles and tests pass
    * Python 3 has a compile error.


References:
  [0] dev@ thread "Python 3 Bindings Query", Troy Curtis.
      https://svn.haxx.se/dev/archive-2017-10/0067.shtml
  [1] https://github.com/encukou/py3c