python3: enforce byte prefix for vfs.open()
Changeset ea8da5aa23c6e723d7f0006387a1a20eef58fc9a added raw prefix to open(),
but also to vfs.open(). The latter only handles bytestring arguments.
mkdir -p html
cp index.html html/
cp *.css html/
cp *.js html/
cp -R img html/
cp -R graphviz-images/ html/
netlify deploy