I noticed this in 2.6, but I imagine it affects 2.7, and 3.x as well.

The documentation for _winreg.OpenKey reads in part:

_winreg.OpenKey(key, sub_key[, res=0][, sam=KEY_READ])

However:

>>> import _winreg
>>> _winreg.OpenKey(_winreg.HKEY_CURRENT_USER, 'Software',
sam=_winreg.KEY_ALL_ACCESS)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: OpenKey() takes no keyword arguments

Probably the OpenKey implementation should be updated to use
PyArg_ParseTupleAndKeywords instead of PyArg_ParseTuple?