This issue appears to have been caused by this commit: https://code.x2go.org/gitweb?p=x2gobroker.git;a=commit;h=f9dd59dd656019f593d37d234a2859cc17696061
This is supported by the fact that I could work around the bug by adding
in the deleted code in a wsgi wrapper script as follows:
# cat /etc/x2go/wsgi/x2gobroker.wsgi
#!/usr/bin/python3
from x2gobroker.loggers import logger_broker, logger_access,
logger_error, tornado_log_request, PROG_NAME
exec(open("/usr/bin/x2gobroker").read())
