Fix tzinfo utcoffset error

[bijlpieter]

Hey all, thank you for the wonderful library!

Since 0.7.3 I started running into tons of errors:

Traceback (most recent call last):
  File "xxx\loguru\_handler.py", line 184, in emit
    formatted = precomputed_format.format_map(formatter_record)
  File "xxx\loguru\_datetime.py", line 140, in __format__
    return _compile_format(fmt)(self)
           ~~~~~~~~~~~~~~~~~~~~^^^^^^
  File "xxx\loguru\_datetime.py", line 23, in _loguru_datetime_formatter
    args = tuple(f(t, dt) for f in formatters)
  File "xxx\loguru\_datetime.py", line 23, in <genexpr>
    args = tuple(f(t, dt) for f in formatters)
                 ~^^^^^^^
  File "xxx\loguru\_datetime.py", line 106, in <lambda>
    "Z": ("%s", lambda t, dt: _format_timezone(dt.tzinfo or timezone.utc, sep=":")),
                              ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "xxx\loguru\_datetime.py", line 40, in _format_timezone
    offset = tzinfo.utcoffset(None).total_seconds()
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'NoneType' object has no attribute 'total_seconds'

Like #856 is requesting, I'm "manually" adding a configurable timezone to my logging:

def tzconverter(record):
    record["time"] = record["time"].astimezone(tz=ZoneInfo("..."))

logger.configure(patcher=tzconverter)

The issue seems to be that the new _format_timezone calls tzinfo.utcoffset with None. And apparently zoneinfo.ZoneInfo objects return None for that input. I think the proper way to handle this would be to instead call tzinfo.utcoffset with the current time.

This PR implements that!

[bijlpieter]

Code coverage CI seems unrelated to my change... let me know if I should have another look

[Delgan]

Oh, thanks a lot for fixing that!

Not sure why the implementation was changed from .utcoffset(dt) to .utcoffset(None) recently, it must have been an oversight. I'll add a few unit tests to avoid any regression in the future.

As a workaround for now, I think the tzconverter() patching function can be updated as follow:

def tzconverter(record):
    zone = ZoneInfo("America/Los_Angeles")
    date = record["time"]
    seconds = zone.utcoffset(date).total_seconds()
    tzinfo = timezone(timedelta(seconds=seconds), zone.tzname(date))
    record["time"] = record["time"].astimezone(tz=tzinfo)

[bijlpieter]

Fantastic Delgan, much appreciated, and happy coding :)