> Previous approach is not applicable to compressobj because
> Py_buffer can't have default value. Seems as compressobj is
> not compatible with Argument Clinic.

Then perhaps we can fix Argument Clinic to be compatible.  Py_buffer doesn't like default values because they mostly don't make sense.  However, I suspect a default value of "None" is fine.  I'll sleep on it and hopefully I can come up with something that will work tomorrow.