http://hg.python.org/cpython/file/be5f1f0bea09/Objects/typeobject.c#l554

CID 486265 (#1 of 1): Unchecked return value (CHECKED_RETURN)
19. check_return: Calling function "PyArg_UnpackTuple(PyObject *, char const *, Py_ssize_t, Py_ssize_t, ...)" without checking return value (as is done elsewhere 64 out of 65 times).
            PyArg_UnpackTuple(PyList_GET_ITEM(temp, i),
                              "", 2, 2, &cls, &mro);