Windows: Simply reuse ctypes existing handle to the Python DLL
Windows: Simply reuse ctypes existing handle to the Python DLL

* This avoids going by name, which apparently also changed for Python3.7
  and made the old code stop working.

* Also in case of an error, make it raise a proper exception instead of
  assertion no error merely.

kayhayen/Nuitka,kayhayen/Nuitka,kayhayen/Nuitka,kayhayen/Nuitka