ci: instructions on how to run the license check

.gitlab-ci.yml

@@ -58,9 +58,17 @@ workflow:
         - ${PRE_COMMIT_HOME}
 
 Check licenses:
-  extends: .common_pre_commit
+  extends:
+    - .colorized
+    - .common_pre_commit
   script:
-    - pre-commit run --color=always --hook-stage manual reuse
+    - |
+      # pre-commit run --hook-stage manual reuse
+      pre-commit run --color=always --hook-stage manual reuse || {
+        printf "${RED}You can reproduce this check locally with \`pre-commit run --hook-stage manual reuse\`.
+      See also ${CI_PROJECT_URL}/-/blob/${CI_DEFAULT_BRANCH}/CONTRIBUTING.md#coding-style.\n${DEFAULT}"
+        exit 1
+      }
   rules:
     - if: $CI_PIPELINE_SOURCE == "web"
       when: manual