Refactor processing lint warnings

Extract out a function to make the code slightly easier to read.

guix-data-service/jobs/load-new-guix-revision.scm

@@ -247,16 +247,8 @@ WHERE job_id = $1"
                                     ',checker-name))
                              %local-checkers))
               (check (lint-checker-check checker)))
-         (filter
-          (match-lambda
-            ((package-id . warnings)
-             (not (null? warnings))))
-          (hash-map->list
-           (lambda (package-id package)
-             (cons
-              package-id
-              (map
-               (lambda (lint-warning)
+
+         (define (process-lint-warning lint-warning)
            (list
             (match (lint-warning-location lint-warning)
               (($ <location> file line column)
@@ -296,6 +288,16 @@ WHERE job_id = $1"
                      (list ,@locales))))
               (cons (cons source-locale source-message)
                     messages-by-locale))))
+
+         (filter
+          (match-lambda
+            ((package-id . warnings)
+             (not (null? warnings))))
+          (hash-map->list
+           (lambda (package-id package)
+             (cons
+              package-id
+              (map process-lint-warning
                    (check package))))
            %package-table)))))