bpo-35059: Enhance _PyObject_AssertFailed() (GH-10642)

Enhance _PyObject_AssertFailed()

* Exchange 'expr' and 'msg' parameters
* 'expr' and 'func' arguments can now be NULL
diff --git a/Lib/test/test_capi.py b/Lib/test/test_capi.py
index 3c8c3f0..7c68b2c 100644
--- a/Lib/test/test_capi.py
+++ b/Lib/test/test_capi.py
@@ -330,7 +330,7 @@
         rc, out, err = assert_python_failure('-c', code)
         self.assertRegex(err,
                          br'_testcapimodule\.c:[0-9]+: '
-                         br'_Py_NegativeRefcount: Assertion ".*" failed; '
+                         br'_Py_NegativeRefcount: Assertion failed: '
                          br'object has negative ref count')