[Python-3000] Interaction between unittest and keyword argument machinery

[Patrick Maupin]

It appears that if a C function is called from Python with **kwargs, a
new dictionary object is created and passed to the C function even if
**kwargs is empty, but if the same C function is called without
**kwargs, then the NULL pointer is passed to the C function.

Because unittest always creates **kwargs, any code path in a C
function which is only executed when the *keywords parameter is NULL
will never be correctly tested from the standard unittest methods.

doctest doesn't have this issue, but appears to be deprecated.  OTOH
unless it would be a major performance hit to never pass empty
*dictionary parameters (always use a NULL pointer) to C functions, it
would remove a whole class of untested potential execution paths to
change the interpreter.

Regards,
Pat