chore: convert warning into error

kenjis · kenjis · commit 776926fa884f · 2022-08-08T21:45:32.000+09:00
diff --git a/.github/workflows/test-userguide.yml b/.github/workflows/test-userguide.yml
@@ -25,3 +25,4 @@ jobs:
       - uses: ammaraskar/sphinx-action@0.4
         with:
           docs-folder: user_guide_src
+          build-command: make html SPHINXOPTS="-W"
