Add tzdata package to add-on timezones

See https://stackoverflow.com/a/78580486/1320237

setup.py

@@ -24,6 +24,7 @@ install_requires = [
     # install requirements depending on python version
     # see https://www.python.org/dev/peps/pep-0508/#environment-markers
     'backports.zoneinfo; python_version == "3.7" or python_version == "3.8"',
+    'tzdata'
 ]
 
 

src/icalendar/tests/test_pytz_zoneinfo_integration.py

@@ -12,5 +12,6 @@ import pytest
 @pytest.mark.parametrize("tzp_", [PYTZ(), ZONEINFO()])
 def test_timezone_names_are_known(tz_name, tzp_):
     """Make sure that all timezones are understood."""
-    pytest.skip()
+    if tz_name in ("Factory", "localtime"):
+        pytest.skip()
     assert tzp_.knows_timezone_id(tz_name), f"{tzp_.__class__.__name__} should know {tz_name}"

src/icalendar/timezone/zoneinfo.py

@@ -25,7 +25,7 @@ class ZONEINFO:
         """Return a timezone with a name or None if we cannot find it."""
         try:
             return zoneinfo.ZoneInfo(name)
-        except ValueError:
+        except zoneinfo.ZoneInfoNotFoundError:
             pass
 
     def knows_timezone_id(self, id: str) -> bool:
@@ -38,6 +38,14 @@ class ZONEINFO:
             # zoninfo does not know any transition dates after 2038
             rrule._until = datetime(2038, 12, 31, tzinfo=pytz.UTC)
 
+    def create_timezone(self, name: str, transition_times, transition_info):
+        """Create a pytz timezone file given information."""
+        cls = type(name, (DstTzInfo,), {
+            'zone': name,
+            '_utc_transition_times': transition_times,
+            '_transition_info': transition_info
+        })
+        return cls()
 
 
 __all__ = ["ZONEINFO"]

tox.ini

@@ -11,7 +11,6 @@ deps =
     pytest
     coverage
     hypothesis
-    backports.zoneinfo ; python_version<'3.9'
 commands =
     coverage run --source=src/icalendar --omit=*/tests/hypothesis/* --omit=*/tests/fuzzed/* --module pytest []
     coverage report