Test building documentation

issue11367
review397811002

.drone.yml

@@ -29,6 +29,11 @@ pipeline:
             - pip install twine
             - python setup.py sdist
             - twine check dist/*
+    check_doc:
+        image: ${IMAGE]
+        commands:
+            - pip install sphinx
+            - python -m sphinx -T -E -W -n -b html doc _build/html
 
 services:
     postgresql: