RFC: fixes python3.10 build of python module - changes to string length in arg parsing

[volca02]

https://python.readthedocs.io/en/stable/c-api/arg.html#strings-and-buffers https://bugs.python.org/issue36381

Recent changes to this made python3.10 build of the python module always fail with non-descriptive error (due to error masking in the argument parsing in ServerProxy constructor).

I'd love to version-guard these changes but for the love of me can't find the version which introduced Py_ssize_t as the valid type to use in these situations. So making this a RFC...