bpo-32384: Skip test when _testcapi isn't available (GH-4940)

(cherry picked from commit 4cc3eb48e1)

Co-authored-by: Isaiah Peng <isaiah@users.noreply.github.com>

Lib/test/test_generators.py

@@ -9,12 +9,18 @@ import inspect
 
 from test import support
 
-_testcapi = support.import_module('_testcapi')
+try:
+    import _testcapi
+except ImportError:
+    _testcapi = None
 
 
 # This tests to make sure that if a SIGINT arrives just before we send into a
 # yield from chain, the KeyboardInterrupt is raised in the innermost
 # generator (see bpo-30039).
+@unittest.skipUnless(_testcapi is not None and
+                     hasattr(_testcapi, "raise_SIGINT_then_send_None"),
+                     "needs _testcapi.raise_SIGINT_then_send_None")
 class SignalAndYieldFromTest(unittest.TestCase):
 
     def generator1(self):