My own fileio implementation fails against the latests versions of the io test suite, under python2.6, because these now require FileIO objects to accept unicode strings in their write methods, whereas the doc mentions raw streams only deal with bytes/bytearrays.

Below is the faulty test (unicode literals or ON). The unicode "xxx" is written to the io.FileIO instance, and the stdlib implementation indeed accepts unicode args (in _fileio.c : "if (!PyArg_ParseTuple(args, "s*", &pbuf)...").

In test_io.py :

   def test_destructor(self):
        record = []
        class MyFileIO(io.FileIO):
            def __del__(self):
                record.append(1)
                io.FileIO.__del__(self)
            def close(self):
                record.append(2)
                io.FileIO.close(self)
            def flush(self):
                record.append(3)
                io.FileIO.flush(self)
        f = MyFileIO(test_support.TESTFN, "w")
        f.write("xxx")
        del f
        self.assertEqual(record, [1, 2, 3])

Hum, it seems that in python2.6, the C API for PyArg_ParseTuple isn't yet ready for bytes and bytearrays, is it ? "y"-like argument parsers don't exist, so I guess we can't easily patch the C api on this, only tests (replacing "xxx" by b"xxx")...

IOTest.test_destructor() is already fixed in Python trunk (future 2.7) by r73394 (Issue #6215: backport the 3.1 io lib).

I don't think that it would be possible to backport the 3.1 io lib in Python 2.6. Would it possible to backport only the io tests?