Fixed in r76372:

* :ref:`pep-3101`.  Note: the 2.6 description mentions the
  :meth:`format` method for both 8-bit and Unicode strings.  In 3.0,
  only the :class:`str` type (text strings with Unicode support)
  supports this method; the :class:`bytes` type does not.  The plan is
  to make this the preferred API for string formatting and to
  de-emphasize the ``%`` string formatting operator.