update for python 3.10

[da4089]

See skarim#184

[htgoebel]

I suggest merging this clause into the next which has a comment about UTC.

[da4089]

I tested a merger of this with the following line, as you suggested. I guess an error from the test suite in branch-0.9:

======================================================================
ERROR: test_pytz_timezone_serializing (__main__.TestIcalendar)
Serializing with timezones from pytz test
----------------------------------------------------------------------
Traceback (most recent call last):
  File "tests.py", line 727, in test_pytz_timezone_serializing
    tz.serialize()
  File "/Users/d/work/personal/vobject-tmp/vobject/base.py", line 258, in serialize
    return behavior.serialize(self, buf, lineLength, validate, *args, **kwargs)
  File "/Users/d/work/personal/vobject-tmp/vobject/behavior.py", line 157, in serialize
    cls.validate(obj, raiseException=True)
  File "/Users/d/work/personal/vobject-tmp/vobject/icalendar.py", line 1073, in validate
    raise ValidateError(m)
vobject.base.ValidateError: 'VTIMEZONE components must contain a valid TZID'

----------------------------------------------------------------------

I haven't had a chance to look into this yet. It's quite possible that the test case is incorrect.

[da4089]

My patch was:

--- a/vobject/icalendar.py
+++ b/vobject/icalendar.py
@@ -332,7 +332,7 @@ class TimezoneComponent(Component):
         """

         # If tzinfo is UTC, we don't need a TZID
-        if tzinfo is None or (not allowUTC and tzinfo_eq(tzinfo, utc)):
+        if tzinfo is None or str(tzinfo) == 'UTC' or (not allowUTC and tzinfo_eq(tzinfo, utc)):
             return None

         # Try pytz tzid key

[htgoebel]

This is strange! Just to exclude a weird case: Have you tried

if str(tzinfo) == 'UTC' of tzinfo is None or (not allowUTC and tzinfo_eq(tzinfo, utc)):