Here's another patch fixes the failing tests. I have tried to support
the buffer attribute using following hack:

        @property
        def buffer(self):
            # XXX Hack to support the buffer attribute.
            buf = codecs.getwriter(self.encoding)(BytesIO(), self.errors)
            value = self.getvalue()
            buf.write(value[:self.tell()])
            pos = buf.stream.tell()
            buf.write(value[self.tell():])
            buf.stream.seek(pos)
            return buf.stream

but this doesn't work since some application might want to modify the
buffer. So, I removed it. Another thing that bothered me were the bogus
encoding and errors arguments. So, I also removed them.