Fix building docker images for dev with Django 2.2

.circleci/config.yml

@@ -23,7 +23,7 @@ commands:
           name: Build docker image and push to repo
           command: |
             docker version
-            docker build -t app:build -f << parameters.dockerfile >> .
+            docker build -t app:build --build-arg DJANGO_VERSION -f << parameters.dockerfile >> .
             docker tag app:build "${DOCKERHUB_REPO}":<< parameters.image_tag >>
             docker login -u "${DOCKERHUB_USER}" -p "${DOCKERHUB_PASS}"
             docker push "${DOCKERHUB_REPO}":<< parameters.image_tag >>

Dockerfile.deploy

@@ -2,6 +2,9 @@ FROM python:3.6-slim-stretch
 
 ENV PYTHON_VERSION_MAJOR 3
 
+ARG DJANGO_VERSION=""
+ENV DJANGO_VERSION=$DJANGO_VERSION
+
 # need to compile swig
 ENV SWIG_FEATURES="-D__x86_64__"