Super fancy error message if assets must be built

.github/workflows/tests.yml

@@ -43,7 +43,7 @@ jobs:
         if: startsWith(matrix.os, 'windows') == false
         run: |
           if ! git diff --exit-code --name-status; then
-            printf '\n\nPLEASE RUN\n\nbin/unipoints build\n'
+            echo "::error file=$(git diff --name-status | head -n1)::PLEASE RUN bin/unipoints build"
             exit 1
           fi
       - name: Check PHP coding style