buildstream2 is not compatible with python 3.11

[jjardon]

Issue for bst1: #1758

[nanonyme]

@gtristan @abderrahim so here we could probably give that grpclib alternative consideration. Looks like Python 3.7+ requirement is fine https://pypi.org/project/BuildStream/

[nanonyme]

BuildStream 2 is now tested on Python 3.11. There is not yet a release with Python 3.11 support. I am hoping since making releases is so hard that the release would also contain fix for #1821

[nanonyme]

This should now be closed.