Reduce image size by approximately 65%

Dockerfile

@@ -3,44 +3,28 @@ FROM debian:buster
 ARG BUILD_SERIES=dev
 ARG BUILD_ID=0
 
-ENV DEBIAN_FRONTEND noninteractive
+COPY requirements.txt /opt/snikket-web-portal/requirements.txt
+COPY build-requirements.txt /opt/snikket-web-portal/build-requirements.txt
+COPY Makefile /opt/snikket-web-portal/Makefile
+COPY snikket_web/ /opt/snikket-web-portal/snikket_web
+COPY babel.cfg /opt/snikket-web-portal/babel.cfg
 
-# This Dockerfile attempts to strike a balance between image size and time it
-# takes to do an incremental build on changes.
-# Improvements welcome.
+WORKDIR /opt/snikket-web-portal
 
 RUN set -eu; \
+    export DEBIAN_FRONTEND=noninteractive ; \
     apt-get update ; \
     apt-get install -y --no-install-recommends \
         python3 python3-pip python3-setuptools python3-wheel \
         libpython3-dev \
         make build-essential \
         ; \
-    apt-get clean ; rm -rf /var/lib/apt/lists
-
-COPY requirements.txt /opt/snikket-web-portal/requirements.txt
-COPY build-requirements.txt /opt/snikket-web-portal/build-requirements.txt
-
-WORKDIR /opt/snikket-web-portal
-
-RUN set -eu; \
     pip3 install -r requirements.txt; \
     pip3 install -r build-requirements.txt; \
-    rm -rf /root/.cache;
-
-COPY Makefile /opt/snikket-web-portal/Makefile
-COPY snikket_web/ /opt/snikket-web-portal/snikket_web
-COPY babel.cfg /opt/snikket-web-portal/babel.cfg
-
-# NOTE: abusing true(1) as a terrible way to disable a specific command. If
-# one merged all the RUN commands into one, one would want to run the
-# uninstall/remove commands there, but with the split up RUN commands it is
-# rather pointless.
-RUN set -eu; \
     make; \
-    true pip3 uninstall -yr build-requirements.txt; \
-    true apt-get remove -y build-essential make libpython3-dev; \
-    true apt-get autoremove -y; \
+    pip3 uninstall -yr build-requirements.txt; \
+    apt-get remove -y build-essential make libpython3-dev; \
+    apt-get autoremove -y; \
     pip3 install hypercorn; \
     rm -rf /root/.cache; \
     apt-get clean ; rm -rf /var/lib/apt/lists