Run cs:check a second time to show diff

Signed-off-by: Daniel Kesselberg <mail@danielkesselberg.de>

.github/workflows/lint.yml

@@ -34,4 +34,7 @@ jobs:
     - name: Install dependencies
       run: composer i
     - name: Run coding standards check
-      run: composer run cs:check -- --format=checkstyle | cs2pr
+      run: |
+        composer run cs:check -- --format=checkstyle | cs2pr
+        composer run cs:check || ( echo 'Please run `composer run cs:fix` to format your code' && exit 1 )
+      shell: bash {0}