> The new patch fixes test_netrc for me but test_csv and test_mailbox are
> still broken.

For test_mailbox at least, I think I have a clue: the _pending member
now contains translated newlines.
But in tell(), we use its length and compare it with the length of a
previous "pending" value stored in self._snapshot...

Can we try to somehow move the replacenl() call inside the _get_chunk
function?
Not sure it will work. This gets more and more obscure...