> In 2.7, PyUnicode_Splitlines() first does:
> string = PyUnicode_FromObject(string);

And it raises an exception if the string contains non-ASCII characters.

It is better to avoid str<->unicode convertion as long as possible. And when 
do it for the output a warning, use "replace" or "backslashreplace" error 
handlers or "latin1" decoder to avoid a failure.