bug#43450: 28.0.50; Python shell doesn't echo if shebang

[Lars Ingebrigtsen <larsi@gnus.org>]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> I can reproduce this in Emacs 28, but it doesn't seem to be triggered by
> the shebang:  Adding some blank lines to the top of the buffer also
> triggers the error.  Or ... anything:
>
> (python-shell-buffer-substring 2 (point) nil)
> => "# -*- coding: utf-8 -*-
>
> 1+2"

I have to admit that I don't understand the reason for the coding cookie
at all -- we bind coding-system-for-write to utf-8 before writing the
temp file anyway, and on the Python side, we specify the coding system
explicitly there, too.

But in case it does have an effect, I haven't removed it altogether, but
instead made the C-c C-e command avoid outputting it, which fixes the
problem.  C-M-x, probably a more important command, is not affected by
the cookie one way or another (since it's just side-effecting), so I've
left it alone there.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no