bug#75065: Upon archive download failure print the original error

[Eli Zaretskii <eliz@gnu.org>]

> From: Konstantin Kharlamov <Hi-Angel@yandex.ru>
> Date: Tue, 24 Dec 2024 18:25:30 +0300
> 
> I was recently helping out a new Emacs user with package installation¹,
> and I found an interesting thing: if you put to `package-archives` a
> URL without `https` prefix, download will fail. Long story short, the
> reason turns out that `package-archives` also supports local paths,
> which the URL being considered as. However, Emacs never prints a
> message about that, even though such message exists in the code.
> Instead it just says that download failed, leaving a user wondering
> why.
> 
> That happens because (package--download-and-read-archives) ignores the
> exception message, and always just prints generic failure message.
> 
> This code fixes this, so now the actual failure message will be
> correctly shown.
> 
> 1:
> https://emacs.stackexchange.com/questions/82828/is-installing-deadgrep-fron-melpa-still-possible/82829#82829
> 
> 
> From fb4685238726a79599f6388318916d2962da93ae Mon Sep 17 00:00:00 2001
> From: Konstantin Kharlamov <Hi-Angel@yandex.ru>
> Date: Tue, 24 Dec 2024 18:16:41 +0300
> Subject: [PATCH] Upon archive download failure print the original error
> 
> * lisp/emacs-lisp/package.el (package--download-and-read-archives):
> upon catching exception, use the exception message as part of the
> error to provide more context about the failure.
> ---
>  lisp/emacs-lisp/package.el | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/lisp/emacs-lisp/package.el b/lisp/emacs-lisp/package.el
> index 5f785071ea3..cb81efc71f0 100644
> --- a/lisp/emacs-lisp/package.el
> +++ b/lisp/emacs-lisp/package.el
> @@ -1829,10 +1829,10 @@ Populate `package-archive-contents' with the result.
>  If optional argument ASYNC is non-nil, perform the downloads
>  asynchronously."
>    (dolist (archive package-archives)
> -    (condition-case-unless-debug nil
> +    (condition-case-unless-debug err
>          (package--download-one-archive archive "archive-contents" async)
> -      (error (message "Failed to download `%s' archive."
> -               (car archive))))))
> +      (error (message "Failed to download `%s' archive. Error: %S"
> +               (car archive) (cdr err))))))
>  
>  (defvar package-refresh-contents-hook (list #'package--download-and-read-archives)
>    "List of functions to call to refresh the package archive.
> -- 
> 2.47.1

Thanks.

Stefan and Philip, is this okay to install?