[python-tulip] StreamWriter.drain(): self._writer does exist or not?

[Victor Stinner]

Hi,

Using Trollius, examples/source1.py fails sometimes with:

   AttributeError: 'StreamWriter' object has no attribute '_writer'

This error comes from StreamWriter.drain():

    if self._reader._exception is not None:
        raise self._writer._exception

I don't see where StreamWriter._writer would be defined. Is it a typo?
(self._writer => self._reader)

I'm unable to reproduce the issue using Tulip. Is this code path
tested by unit tests?

Victor