textiowrapper_interlaced_read_write.patch: TextIOWrapper.write() calls self.seek(self.tell()) if it has a decoder or if snapshot is not None.

I suppose that we can do better, but at least it does fix this issue.

"read(); write(); write()" only calls self.seek(self.tell()) once, at the first write. So I don't think that it changes anything with performances.

In which case snapshot can be not different than None, whereas decoder is None?