create missing pytz.UnknownTimeZoneError

src/icalendar/tests/test_equality.py

@@ -4,9 +4,10 @@
 import copy
 
 try:
-    import pytz
+    from pytz import UnknownTimeZoneError
 except ImportError:
-    pytz = None
+    class UnknownTimeZoneError(Exception):
+        pass
 from datetime import date, datetime, time, timedelta
 
 import pytest
@@ -82,9 +83,9 @@ def test_deep_copies_are_equal(ics_file, tzp):
     Ignore errors when a custom time zone is used.
     This is still covered by the parsing test.
     """
-    with contextlib.suppress(pytz.UnknownTimeZoneError):
+    with contextlib.suppress(UnknownTimeZoneError):
         assert_equal(copy.deepcopy(ics_file), copy.deepcopy(ics_file))
-    with contextlib.suppress(pytz.UnknownTimeZoneError):
+    with contextlib.suppress(UnknownTimeZoneError):
         assert_equal(copy.deepcopy(ics_file), ics_file)