Dealing with unknown timezones

[sebix]

If the server's zoneinfo has no information about the timezone, dateutil just raises a warning.
In this example, the server is a Debian 11 Docker container, the server does not know about CEST:

>>> import dateutil.parser
>>> dateutil.parser.parse('Tue 12 Jul 2022 10:47:47 AM CEST', fuzzy=True)
/usr/local/lib/python3.8/dist-packages/dateutil/parser/_parser.py:1207: UnknownTimezoneWarning: tzname CEST identified but not understood.  Pass `tzinfos` argument in order to correctly return a timezone-aware datetime.  In a future version, this will raise an exception.
  warnings.warn("tzname {tzname} identified but not understood.  "
datetime.datetime(2022, 7, 12, 10, 47, 47)

On other systems, CEST is known, so it's not a defect of dateutil or pytz. Maybe it depends on the pytz installation method (if installed from packages/the distribution, the distro's zoneinfo is used, otherwise the built-in timezone infos, which may have a different (smaller) data base).

I suggest to raise an error if the timezone is found, but not unterstood, i.e. converting the warning to an exception.