Issue #20532: Tests which use _testcapi now are marked as CPython only.
diff --git a/Lib/test/test_threading.py b/Lib/test/test_threading.py
index 41be68e..1653d36 100644
--- a/Lib/test/test_threading.py
+++ b/Lib/test/test_threading.py
@@ -1,7 +1,7 @@
 # Very rudimentary test of threading module
 
 import test.test_support
-from test.test_support import verbose
+from test.test_support import verbose, cpython_only
 from test.script_helper import assert_python_ok
 
 import random
@@ -724,6 +724,7 @@
         for t in threads:
             t.join()
 
+    @cpython_only
     @unittest.skipIf(_testcapi is None, "need _testcapi module")
     def test_frame_tstate_tracing(self):
         # Issue #14432: Crash when a generator is created in a C thread that is