now stricter in rejecting excess arguments.  The only time when
  either allows excess arguments is when it is not overridden and the
  other one is.  For backwards compatibility, when both are
  overridden, it is a deprecation warning (for now; maybe a Py3k
  warning later).

When merging this into 3.0, the warnings should become errors.

Note: without the change to string.py, lots of spurious warnings happen.
What's going on there?