[3.15] gh-120965: Skip test_zoneinfo.ExtensionBuiltTest if C extension is not available (GH-131104) (#160470)

(cherry picked from commit 897671b)

Co-authored-by: Stan Ulbrych <stan@python.org>
Co-authored-by: Paul Ganssle <1377457+pganssle@users.noreply.github.com>

Author: 3 people

Lib/test/test_zoneinfo/test_zoneinfo.py

@@ -12,6 +12,7 @@
 import re
 import shutil
 import struct
+import sys
 import tempfile
 import unittest
 from datetime import date, datetime, time, timedelta, timezone
@@ -2201,6 +2202,8 @@ def test_pydatetime(self):
             PYTHONTZPATH=str(ZONEINFO_DATA.tzpath))
 
 
+@unittest.skipIf(sys.modules.get("_zoneinfo") is None,
+                 "_zoneinfo C module not available")
 class ExtensionBuiltTest(unittest.TestCase):
     """Smoke test to ensure that the C and Python extensions are both tested.