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

[Stefan Kangas <stefankangas@gmail.com>]

Konstantin Kharlamov <Hi-Angel@yandex.ru> writes:

> On Thu, 2024-12-26 at 14:17 -0500, Stefan Monnier wrote:
>> > > >    (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))))))
>> > > >
>> > > Stefan and Philip, is this okay to install?
>>
>> I agree with the idea behind the patch, but printing just `(cdr err)`
>> doesn't seem right, it should print the whole of `err`.
>
> The `car` seems to just contain word error. Here's how both compare:
>
> • current patch with `(cdr err)`:
>     Failed to download ‘melpa’ archive. Error: ("Location melpa.org/packages/ is not a url nor an absolute file name")
>
> • suggested change with `err`:
>     Failed to download ‘melpa’ archive. Error: (error "Location melpa.org/packages/ is not a url nor an absolute file name")

The "Error:" part is redundant, so I think it could be shortened to
something like:

    Failed to download ‘melpa’ archive: Location melpa.org/packages/ is
    not a url nor an absolute file name