[3.9] bpo-37116: Use PEP 570 syntax for positional-only parameters. (GH-12620)

Turn deprecation warnings added in 3.8 into TypeError.
diff --git a/Lib/test/test_trace.py b/Lib/test/test_trace.py
index 4bc21ea..912badb 100644
--- a/Lib/test/test_trace.py
+++ b/Lib/test/test_trace.py
@@ -276,9 +276,8 @@
     def test_arg_errors(self):
         res = self.tracer.runfunc(traced_capturer, 1, 2, self=3, func=4)
         self.assertEqual(res, ((1, 2), {'self': 3, 'func': 4}))
-        with self.assertWarns(DeprecationWarning):
-            res = self.tracer.runfunc(func=traced_capturer, arg=1)
-        self.assertEqual(res, ((), {'arg': 1}))
+        with self.assertRaises(TypeError):
+            self.tracer.runfunc(func=traced_capturer, arg=1)
         with self.assertRaises(TypeError):
             self.tracer.runfunc()