I ran the the following, which I don't understand, and therefore don't what should happen, on Win 10, 3.6.0a3.

from ctypes import *
from ctypes.wintypes import *

class CustomPHKEY(object):
    def __init__(self, value):
        self._as_parameter_ = HKEY(value)

function = windll.function
function.argtypes = [POINTER(HKEY)]
function.restype = LONG
result = CustomPHKEY(0)
function(result)

Traceback (most recent call last):
  File "F:\Python\mypy\tem.py", line 8, in <module>
    function = windll.function
  File "C:\Programs\Python36\lib\ctypes\__init__.py", line 417, in __getattr__
    dll = self._dlltype(name)
  File "C:\Programs\Python36\lib\ctypes\__init__.py", line 347, in __init__
    self._handle = _dlopen(self._name, mode)
OSError: [WinError 126] The specified module could not be found