Dev docker tweaks

backend/dev-docker/Dockerfile

@@ -1,4 +1,14 @@
-FROM python:3.8-buster
+FROM python:3.8-slim
+
+# https://stackoverflow.com/questions/58701233/docker-logs-erroneously-appears-empty-until-container-stops
+ENV PYTHONUNBUFFERED=1
+
+COPY requirements.txt /tmp/requirements.txt
+RUN pip3 install -r /tmp/requirements.txt
+
+
+RUN [ ! -d "/datastore" ] && mkdir /datastore
+
 COPY sleep.py /
 CMD [ "python", "/sleep.py" ]