on 4.2.21, setup.py doesn't work with python3.11

[DamienWykland]

Hello !

Describe the bug

Rocky 8.8 is now shipped with python3.11 so I tried to build exabgp 4.2.21 with python3.11 on my CI.
However it's failing with error :
ModuleNotFoundError: No module named 'setuptools'

I tried installing the mentionned package manually but it doesn't help.

** To reproduce **
Try to build exabgp 4.2.21 with python3.11

Environment (please complete the following information):
c

• OS: [Rocky Linux 8.8]
• Version [ exabgp 4.2.21, python3.11]