Dockerfile update (#644)

- Updated images with newer versions, except for Node: the js stuff will not compile with a version > 10
- Removed python3-dev and sqlite3 in step 2, they are not needed
- Added flask to pip, cf. issue #621
- Some small improvements here and there like a good practice for gunicorn use in Docker cf. https://pythonspeed.com/articles/gunicorn-in-docker/

Dockerfile

@@ -1,22 +1,23 @@
 # First, compile JS stuff
-FROM node
+FROM node:dubnium-buster
 WORKDIR /src/
 COPY . .
-RUN npm install -g requirejs uglify-js jade bower
-RUN make init js
+RUN npm install -g requirejs uglify-js jade bower \
+ && make init js
 
 # Second, create virtualenv
-FROM python:3-stretch
+FROM python:3.8-buster
 WORKDIR /src/
 COPY --from=0 /src .
-RUN apt-get -qqy update && apt-get -qqy install python3-dev sqlite3
 RUN python3 -m venv /isso \
  && . /isso/bin/activate \
- && pip install gunicorn cffi \
- && python setup.py install
+ && pip3 install --no-cache-dir --upgrade pip \
+ && pip3 install --no-cache-dir gunicorn cffi flask \
+ && python setup.py install \
+ && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
 
 # Third, create final repository
-FROM python:3-slim-stretch
+FROM python:3.8-slim-buster
 WORKDIR /isso/
 COPY --from=1 /isso .
 
@@ -24,7 +25,7 @@ COPY --from=1 /isso .
 VOLUME /db /config
 EXPOSE 8080
 ENV ISSO_SETTINGS /config/isso.cfg
-CMD ["/isso/bin/gunicorn", "-b", "0.0.0.0:8080", "-w", "4", "--preload", "isso.run"]
+CMD ["/isso/bin/gunicorn", "-b", "0.0.0.0:8080", "-w", "4", "--preload", "isso.run", "--worker-tmp-dir", "/dev/shm"]
 
 # Example of use:
 #