be robust against test being run over and over (such as -R)

Modules/_testcapimodule.c

@@ -1144,13 +1144,23 @@ raise_exception(PyObject *self, PyObject *args)
 	return NULL;
 }
 
+
+static int test_run_counter = 0;
+
 static PyObject *
 test_datetime_capi(PyObject *self, PyObject *args) {
 	if (PyDateTimeAPI) {
-		PyErr_SetString(PyExc_AssertionError,
-				"PyDateTime_CAPI somehow initialized");
-		return NULL;
+		if (test_run_counter) {
+			/* Probably regrtest.py -R */
+			Py_RETURN_NONE;
+		}
+		else {
+			PyErr_SetString(PyExc_AssertionError,
+					"PyDateTime_CAPI somehow initialized");
+			return NULL;
+		}
 	}
+	test_run_counter++;
 	PyDateTime_IMPORT;
         if (PyDateTimeAPI)
 		Py_RETURN_NONE;