Use 'formatted-message' instead of '&message' where appropriate.

* gnu.scm (%try-use-modules): Use 'formatted-message' instead of
'&message'.
* gnu/machine/digital-ocean.scm (maybe-raise-unsupported-configuration-error):
Likewise.
* gnu/machine/ssh.scm (machine-check-file-system-availability): Likewise.
(machine-check-building-for-appropriate-system): Likewise.
(deploy-managed-host): Likewise.
(maybe-raise-unsupported-configuration-error): Likewise.
* gnu/packages.scm (search-patch): Likewise.
* gnu/services.scm (%service-with-default-value): Likewise.
(files->etc-directory): Likewise.
(fold-services): Likewise.
* gnu/system.scm (locale-name->definition*): Likewise.
* gnu/system/mapped-devices.scm (check-device-initrd-modules): Likewise.
(check-luks-device): Likewise.
* guix/channels.scm (latest-channel-instance): Likewise.
* guix/cve.scm (json->cve-items): Likewise.
* guix/git-authenticate.scm (commit-signing-key): Likewise.
(commit-authorized-keys): Likewise.
(authenticate-commit): Likewise.
(verify-introductory-commit): Likewise.
* guix/remote.scm (remote-pipe-for-gexp): Likewise.
* guix/scripts/graph.scm (assert-package): Likewise.
* guix/scripts/offload.scm (private-key-from-file*): Likewise.
* guix/ssh.scm (authenticate-server*): Likewise.
(open-ssh-session): Likewise.
(remote-inferior): Likewise.
* guix/ui.scm (matching-generations): Likewise.
* guix/upstream.scm (package-update): Likewise.
* tests/channels.scm ("latest-channel-instances, missing introduction for 'guix'"):
Catch 'formatted-message?'.
("authenticate-channel, wrong first commit signer"): Likewise.
* tests/lint.scm ("patches: not found"): Adjust message string.
* tests/packages.scm ("patch not found yields a run-time error"): Catch
'formatted-message?'.
* guix/lint.scm (check-patch-file-names): Handle 'formatted-message?'.
(check-derivation): Ditto.

gnu/machine/digital-ocean.scm

@@ -26,6 +26,7 @@
   #:use-module (guix base32)
   #:use-module (guix derivations)
   #:use-module (guix i18n)
+  #:use-module ((guix diagnostics) #:select (formatted-message))
   #:use-module (guix import json)
   #:use-module (guix monads)
   #:use-module (guix records)
@@ -414,9 +415,7 @@ one procured from https://cloud.digitalocean.com/account/api/tokens.")))))))
   (let ((config (machine-configuration machine))
         (environment (environment-type-name (machine-environment machine))))
     (unless (and config (digital-ocean-configuration? config))
-      (raise (condition
-              (&message
-               (message (format #f (G_ "unsupported machine configuration '~a'
+      (raise (formatted-message (G_ "unsupported machine configuration '~a' \
 for environment of type '~a'")
                                 config
-                                environment))))))))
+                                environment)))))