bpo-39825: Fixes sysconfig.get_config_var('EXT_SUFFIX') on Windows to match distutils (GH-22088)

diff --git a/Lib/test/test_sysconfig.py b/Lib/test/test_sysconfig.py
index d07d28d..352dbde 100644
--- a/Lib/test/test_sysconfig.py
+++ b/Lib/test/test_sysconfig.py
@@ -360,10 +360,12 @@ def test_SO_value(self):
 
     @unittest.skipIf(sysconfig.get_config_var('EXT_SUFFIX') is None,
                      'EXT_SUFFIX required for this test')
-    def test_SO_in_vars(self):
+    def test_EXT_SUFFIX_in_vars(self):
+        import _imp
         vars = sysconfig.get_config_vars()
         self.assertIsNotNone(vars['SO'])
         self.assertEqual(vars['SO'], vars['EXT_SUFFIX'])
+        self.assertEqual(vars['EXT_SUFFIX'], _imp.extension_suffixes()[0])
 
     @unittest.skipUnless(sys.platform == 'linux' and
                          hasattr(sys.implementation, '_multiarch'),