Download fonts at app startup instead

We can't bake the font into the Docker image as such, because we mount
the volumes which blows away anything we have in the app tree
beforehand.

We could stash it somewhere in the image and then copy it from there on
app startup or something, but at that point we might as well just
download it as part of the app startup.

Dockerfile

@@ -6,13 +6,6 @@ RUN mkdir /app /app/static /app/images
 
 WORKDIR /app
 
-# Use RUN curl because ADD will re-download the file every time to make sure it
-# hasn't changed, which is exactly what we don't want
-RUN mkdir -p /app/static/fonts/source_han_sans
-RUN curl \
-  https://github.com/adobe-fonts/source-han-sans/raw/release/Variable/OTC/SourceHanSans-VF.ttf.ttc \
-  -o /app/static/fonts/source_han_sans/SourceHanSans-VF.ttf.ttc
-
 COPY requirements.txt /app/
 RUN pip install -r requirements.txt --no-cache-dir
 RUN apt-get update && apt-get install -y gettext libgettextpo-dev tidy && apt-get clean