bug#65870: 30.0.50; Error in python-mode when try to delete a character in badly-indented code

[Eli Zaretskii <eliz@gnu.org>]

> Date: Mon, 11 Sep 2023 17:36:59 +0100
> From: Daniel Lopez <daniel.lopez999@gmail.com>
> 
> To reproduce from emacs -Q:
>   C-x b hello.py RET
>   M-x python-mode
>   On the first line, type the word "return", then press the Return key.
>   On the second line, type one or more spaces.
>   Press Backspace. This triggers the error message:
>       python-indent-line: Wrong type argument: wholenump, -4
>   and, the last-typed space is not deleted.
> 
> Backtrace of the error:
>   Debugger entered--Lisp error: (wrong-type-argument wholenump -4)
>     indent-line-to(-4)
>     python-indent-line(t)
>     python-indent-dedent-line()
>     python-indent-dedent-line-backspace(1)
>     funcall-interactively(python-indent-dedent-line-backspace 1)
>     command-execute(python-indent-dedent-line-backspace)
> 
> This can also happen with Python keywords/statements that tend to end a
> scope, eg. "break" or "raise", as well as "return".
> 
> I guess the smart dedenting sees the "return" (or similar statement) at
> top-level scope and then tries to move the cursor to a parent scope /
> negative column that doesn't exist. Perhaps one of those indent
> functions could clamp itself somehow to not do that but I'm not sure
> where the best place for that would be.

Thanks.

kobarity, any suggestions or comments?