Fix description of range_length_obj

Objects/rangeobject.c

@@ -126,10 +126,9 @@ range_dealloc(rangeobject *r)
     PyObject_Del(r);
 }
 
-/* Return number of items in range (lo, hi, step), when arguments are PyLong
- * objects.  Return a value < 0 if & only if the true value is too large to
- * fit in a signed long.  Arguments MUST return 1 with PyLong_Check().  Return
- * -1 when there is an error.
+/* Return number of items in range (lo, hi, step) as a PyLong object,
+ * when arguments are PyLong objects.  Arguments MUST return 1 with
+ * PyLong_Check().  Return NULL when there is an error.
  */
 static PyObject*
 range_length_obj(rangeobject *r)