bug#19744: 25.0.50; Cannot yank text with "\n" in inferior python mode

[Dima Kogan]

Hi.

I'm using a very recent build of Emacs from git. Trying to yank any text
with a "\n" in it into an inferior python buffer does not work: no text
is yanked at all. To reproduce:

1. emacs -Q
2. M-x run-python
3. Type and kill "5\n"
4. C-y. Nothing happens.

If in step 3 you kill "5" instead, then the yank works fine. This is due
to the python-shell-font-lock-post-command-hook. There, the just-entered
input is deleted, and re-inserted with proper fontification. Except in
this case the re-insertion doesn't work for some reason. I'll look later
myself if nobody else get to it first.