bpo-28280: Make PyMapping_Keys(), PyMapping_Values() and PyMapping_Items() always return a list (#3840)

Modules/_testcapimodule.c

@@ -4306,6 +4306,25 @@ py_w_stopcode(PyObject *self, PyObject *args)
 #endif
 
 
+static PyObject *
+get_mapping_keys(PyObject* self, PyObject *obj)
+{
+    return PyMapping_Keys(obj);
+}
+
+static PyObject *
+get_mapping_values(PyObject* self, PyObject *obj)
+{
+    return PyMapping_Values(obj);
+}
+
+static PyObject *
+get_mapping_items(PyObject* self, PyObject *obj)
+{
+    return PyMapping_Items(obj);
+}
+
+
 static PyObject *
 test_pythread_tss_key_state(PyObject *self, PyObject *args)
 {
@@ -4573,6 +4592,9 @@ static PyMethodDef TestMethods[] = {
 #ifdef W_STOPCODE
     {"W_STOPCODE", py_w_stopcode, METH_VARARGS},
 #endif
+    {"get_mapping_keys", get_mapping_keys, METH_O},
+    {"get_mapping_values", get_mapping_values, METH_O},
+    {"get_mapping_items", get_mapping_items, METH_O},
     {"test_pythread_tss_key_state", test_pythread_tss_key_state, METH_VARARGS},
     {NULL, NULL} /* sentinel */
 };