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

[Stefan Monnier via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

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> `%s` to print `err` or `(cdr err)` would be wrong, since `%s` is for use
> with strings rather than lists.  IOW, IMO, it should be either
>
>     ...%S" ... err)
>
> or
>
>     ...%s" ... (error-message-string err))
>
> where the first is a bit more "debugging/developer" friendly and the second
> is a bit more "user" friendly.

Revising the code of `package.el` I see that those errors&messages are
meant to be exposed to the user, so they should preferably use
`error-message-string`.

So I installed the patch below into `master`.
Thank you!
Closing,


        Stefan

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commit a99e1cc745047977b0b7cbd25fe9df66e9c86a39
Author: Stefan Monnier <monnier@iro.umontreal.ca>
Date:   Fri Dec 27 11:58:30 2024 -0500

    (package--download-and-read-archives): Fix bug#75065
    
    * lisp/emacs-lisp/package.el (package--download-and-read-archives):
    Include the error info in the error message.
    Suggested by Konstantin Kharlamov <Hi-Angel@yandex.ru>.
    (package-refresh-contents, package-menu--perform-transaction):
    Use `error-message-string`.

diff --git a/lisp/emacs-lisp/package.el b/lisp/emacs-lisp/package.el
index 5f785071ea3..bff45d57b07 100644
--- a/lisp/emacs-lisp/package.el
+++ b/lisp/emacs-lisp/package.el
@@ -1829,10 +1829,11 @@ package--download-and-read-archives
 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: %s"
+                      (car archive)
+                      (error-message-string err))))))
 
 (defvar package-refresh-contents-hook (list #'package--download-and-read-archives)
   "List of functions to call to refresh the package archive.
@@ -1856,7 +1857,8 @@ package-refresh-contents
     (when (and (package-check-signature) (file-exists-p default-keyring))
       (condition-case-unless-debug error
           (package-import-keyring default-keyring)
-        (error (message "Cannot import default keyring: %S" (cdr error))))))
+        (error (message "Cannot import default keyring: %s"
+                        (error-message-string error))))))
   (run-hook-with-args 'package-refresh-contents-hook async))
 
 \f
@@ -3989,8 +3991,9 @@ package-menu--perform-transaction
               (package-delete elt nil 'nosave))
           (error
            (push (package-desc-full-name elt) errors)
-           (message "Error trying to delete `%s': %S"
-                    (package-desc-full-name elt) err)))))
+           (message "Error trying to delete `%s': %s"
+                    (package-desc-full-name elt)
+                    (error-message-string err))))))
     errors))
 
 (defun package--update-selected-packages (add remove)