adapt to changes in Python 3.10

[anarcat]

It looks like the qrencode Python library is currently unusable in Debian bookworm. Here's a simple example:

anarcat@angela:paperbackup$ python3 -c 'import qrencode ; version, size, data = qrencode.encode(b"test")' Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/lib/python3/dist-packages/qrencode/__init__.py", line 47, in encode
    version, size, data = _encode(data, version, level, hint, True)
                          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
SystemError: PY_SSIZE_T_CLEAN macro must be defined for '#' formats anarcat@angela:paperbackup[1]$

According to a casual search on the web, it looks like the extension needs to be recompiled / patched for Python 3.10:

https://stackoverflow.com/a/71019907

Quote:

On 3.10 any module(s) that use the # variant when parsing arguments need to have a #define PY_SSIZE_T_CLEAN before including Python.h.

I don't actually know what I'm doing here to be real honest, but that fixes the problem on my end.