Make sphinx-build free of warnings

Instruct sphinx to treat all warnings as errors in the CI build.

Author: maarten-ic

docs/source/conf.py

@@ -247,7 +247,7 @@
 # The name of an image file (within the static path) to use as favicon of the
 # docs.  This file should be a Windows icon file (.ico) being 16x16 or 32x32
 # pixels large.
-html_favicon = "_static/favicon.ico"
+# html_favicon = "_static/favicon.ico"
 
 # Add any paths that contain custom static files (such as style sheets) here,
 # relative to this directory. They are copied after the builtin static files,

envs/common/80_build_docs.sh

@@ -18,4 +18,6 @@ $PIP freeze
 
 # Use the sphinx matching the venv we are in using SPHINXBUILD
 VENV_SPHINX_BUILD='../venv_imaspy/bin/sphinx-build'
+# Instruct sphinx to treat all warnings as errors
+export SPHINXOPTS='-W --keep-going'
 make -C docs html SPHINXBUILD="$PYTHON $VENV_SPHINX_BUILD"