Dockerfile: apt-get --assume-yes to prevent build from stalling

Author: Bjwebb

Dockerfile

@@ -19,7 +19,7 @@ RUN git config --global --add safe.directory /app
 # Build our own copy of lxml using Ubuntu's libxml2/libxslt
 # (don't use the prebuilt wheel)
 # https://opendataservices.plan.io/issues/36790
-RUN apt install libxml2-dev libxslt-dev
+RUN apt-get --assume-yes install libxml2-dev libxslt-dev
 RUN pip install --no-binary lxml -r requirements.txt
 
 RUN python manage.py collectstatic --noinput