[3.12] gh-113027: Fix test_variable_tzname in test_email (GH-113821) (GH-113831)

Determine the support of the Kyiv timezone by checking the result of
astimezone() which uses the system tz database and not the one
populated by zoneinfo.
(cherry picked from commit 931d7e0)

Co-authored-by: Serhiy Storchaka <[email protected]>

Author: miss-islington

Lib/test/test_email/test_utils.py

@@ -143,12 +143,12 @@ def test_localtime_epoch_notz_daylight_false(self):
         t2 = utils.localtime(t0.replace(tzinfo=None))
         self.assertEqual(t1, t2)
 
-    @unittest.skipUnless("Europe/Kyiv" in zoneinfo.available_timezones(),
-                         "Can't find a Kyiv timezone database")
     @test.support.run_with_tz('Europe/Kyiv')
     def test_variable_tzname(self):
         t0 = datetime.datetime(1984, 1, 1, tzinfo=datetime.timezone.utc)
         t1 = utils.localtime(t0)
+        if t1.tzname() in ('Europe', 'UTC'):
+            self.skipTest("Can't find a Kyiv timezone database")
         self.assertEqual(t1.tzname(), 'MSK')
         t0 = datetime.datetime(1994, 1, 1, tzinfo=datetime.timezone.utc)
         t1 = utils.localtime(t0)