This is probably not a bug in python, but a change in system behaviour.

In particular, I've used the lsof command to check the open files for the syslogd proces on a macOS 10.13 and 12.2 system. On the former syslogd has /var/run/syslog open, on the latter it doesn't.

The feature to listen on this socket has been removed entirely, the 12.2 system no longer lists a "-bsd_in" option for syslogd in the manual page whereas it is both available and enabled by default on 10.13.

It might be possible to change the SyslogHandler to optionally use the syslog module to log, but I'm not sure it is worth doing this and that would definitely be a new feature.