Check links in CI with htmlcheck

Remove test_links.py

.gitlab-ci.yml

@@ -1,28 +1,43 @@
 variables:
   GIT_SUBMODULE_STRATEGY: recursive
 
-test-links:
-  image: python:latest
-  script:
-    - python3 ./test_links.py
+## GitLab defaults to:
+# stages:
+# - build
+# - test
+# - deploy
 
-test-trailing-spaces:
-  script:
-    - ./test_trailing_spaces.sh
-
-test-build:
-  image: registry.gitlab.com/pages/hugo/hugo_extended
-  script:
-  - hugo
-  except:
-  - main
-
-pages:
+build-site:
+  stage: build
   image: registry.gitlab.com/pages/hugo/hugo_extended
   script:
     - hugo
   artifacts:
     paths:
-    - public
+      - public
+
+test-html:
+  stage: test
+  image:
+    name: wjdp/htmltest:latest
+    entrypoint: [""]
+  cache:
+    key: htmltest-cache
+    paths:
+      - tmp/
+  script:
+    - htmltest
+
+test-trailing-spaces:
+  stage: test
+  needs: [] # ok to run before build-site
+  script:
+    - ./test_trailing_spaces.sh
+
+# The GitLab Pages job must always be named "pages", and result in a "public" artifact.
+# Our "public" artifact is created above, but GitLab jobs will fetch all artifacts from previous stages.
+pages:
+  stage: deploy
+  script: ls -ld public
   only:
-  - main
+    - main