How u can see above: the file client.py is referenced about /usr/lib/python3.8/http but all other files descripted in the email are referenced about /usr/lib/python3/dist-packages/... But in /usr/lib/python3/ the directory and the file client.py is missing. Can this be the problem?
No, Python has a search path, so not all code needs to be in the same place. It appears that ResponseNotReady is being raised in that file, anyway, so that's not the problem.
Unfortunately, I am not familiar with that code, so that's the most I can say until I have time to study it. Perhaps somebody else will pick it up in the meantime.