dateutil does not compute DST right
The cron timezone tests fails on Python version without ZoneInfo: https://drone.tryton.org/tryton/trytond/1252/10 The reason is that dateutil does not compute the ambiguity of datetime correctly see: https://www.tryton.org/~irclog/2022-10-03.log.html#t10:10. As it is only for old Python version, I think the simplest solution is to skip the test.