deploy: Let key-and-args exceptions through.

Fixes <https://bugs.gnu.org/44825>.
Reported by Christopher Lemmer Webber <cwebber@dustycloud.org>.

* guix/ui.scm (guard*): Export.
* guix/scripts/deploy.scm (deploy-machine*): Use 'guard*' instead of
'guard'.  Add '&exception-with-kind-and-args' case.

guix/scripts/deploy.scm

@@ -120,7 +120,18 @@ (define (deploy-machine* store machine)
   (info (G_ "deploying to ~a...~%")
         (machine-display-name machine))
 
-  (guard (c ((message-condition? c)
+  (guard* (c
+           ;; On Guile 3.0, exceptions such as 'unbound-variable' are compound
+           ;; and include a '&message'.  However, that message only contains
+           ;; the format string.  Thus, special-case it here to avoid
+           ;; displaying a bare format string.
+           ((cond-expand
+              (guile-3
+               ((exception-predicate &exception-with-kind-and-args) c))
+              (else #f))
+            (raise c))
+
+           ((message-condition? c)
             (report-error (G_ "failed to deploy ~a: ~a~%")
                           (machine-display-name machine)
                           (condition-message c)))

guix/ui.scm

@@ -101,6 +101,7 @@ (define-module (guix ui)
             show-what-to-build
             show-what-to-build*
             show-manifest-transaction
+            guard*
             call-with-error-handling
             with-error-handling
             with-unbound-variable-handling