Parameterize the Debian version

.circleci/Dockerfile.debian

@@ -1,4 +1,5 @@
-FROM debian:8
+ARG TAG
+FROM debian:${TAG}
 
 ENV WHEELHOUSE_PATH /tmp/wheelhouse
 ENV VIRTUALENV_PATH /tmp/venv

.circleci/Dockerfile.debian-9

@@ -1,24 +0,0 @@
-FROM debian:9
-
-ENV WHEELHOUSE_PATH /tmp/wheelhouse
-ENV VIRTUALENV_PATH /tmp/venv
-# This will get updated by the CircleCI checkout step.
-ENV BUILD_SRC_ROOT /tmp/project
-
-RUN apt-get --quiet update && \
-    apt-get --quiet --yes install git && \
-    apt-get --quiet --yes install \
-        sudo \
-    	build-essential \
-	python2.7 \
-    	python2.7-dev \
-    	libffi-dev \
-    	libssl-dev \
-    	libyaml-dev \
-    	virtualenv
-
-# Get the project source.  Copying in the whole project source here isn't very
-# cache friendly but there's no Docker layer cache on CircleCI anyway!
-COPY . ${BUILD_SRC_ROOT}
-
-RUN "${BUILD_SRC_ROOT}"/.circleci/prepare-image.sh "${WHEELHOUSE_PATH}" "${VIRTUALENV_PATH}" "${BUILD_SRC_ROOT}"

.circleci/config.yml

@@ -366,8 +366,8 @@ jobs:
       - run:
           name: "Build Debian images"
           command: |
-            docker build -t tahoelafsci/debian:8 -f ~/project/.circleci/Dockerfile.debian-8 ~/project/
-            docker build -t tahoelafsci/debian:9 -f ~/project/.circleci/Dockerfile.debian-9 ~/project/
+            docker build --build-arg TAG=8 -t tahoelafsci/debian:8 -f ~/project/.circleci/Dockerfile.debian ~/project/
+            docker build --build-arg TAG=9 -t tahoelafsci/debian:9 -f ~/project/.circleci/Dockerfile.debian ~/project/
       - run:
           name: "Push Debian images"
           command: |