Use correct requirements when building docs and turn warnings into errors

Author: finsberg

.github/workflows/build_docs.yml

@@ -36,7 +36,7 @@ jobs:
         run: python3 -m pip install -r requirements-docs.txt
 
       - name: Build docs
-        run: jupyter book build .
+        run: jupyter book build -W .
 
 
       - name: Cache