PY_SSIZE_T_CLEAN macro must be defined for '#' formats

[~j0ule]

A new python3 has been released and it caused a breaking change in 3.10

Traceback (most recent call last):
  File "/mnt/disk0/Users/user/Nextcloud/PC-SYNC/Projects/_source_codes/github/mdns-debugger/mdns-debugger.py", line 464, in <module>
    (header, packet) = cap.next()
SystemError: PY_SSIZE_T_CLEAN macro must be defined for '#' formats