KeyError: TZID

[SnarkBoojum]

Until recently 1.9.2 was compiling perfectly in Debian ; but now there is a failing test:

ERROR: test_timezone (django_ical.tests.test_feed.ICal20FeedTest.test_timezone)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/<<PKGBUILDDIR>>/django_ical/tests/test_feed.py", line 490, in test_timezone
    self.assertEqual(calendar.subcomponents[1]["DTSTART"].params["TZID"], "EDT")
                     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^^^^^^^^
  File "/usr/lib/python3/dist-packages/icalendar/caselessdict.py", line 40, in __getitem__
    return super().__getitem__(key.upper())
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
KeyError: 'TZID'

I suspect some test file changed and this test was using something that disappeared, but I haven't been able to track down precisely what happened where.