Bake docker-ce into the base image

Speeds up CI runs by quite a bit

.circleci/base-image/Dockerfile

@@ -0,0 +1,22 @@
+FROM continuumio/miniconda3:4.5.4
+
+
+RUN apt-get update --yes
+
+RUN apt-get install --yes --no-install-recommends \
+        apt-transport-https \
+        ca-certificates \
+        curl \
+        gnupg2 \
+        software-properties-common
+
+RUN curl -fsSL https://download.docker.com/linux/debian/gpg | apt-key add -
+
+RUN add-apt-repository \
+        "deb [arch=amd64] https://download.docker.com/linux/debian \
+        $(lsb_release -cs) \
+        stable"
+
+RUN apt-get update --yes
+
+RUN apt-get install --yes  docker-ce

.circleci/base-image/README.rst

@@ -0,0 +1,16 @@
+========================
+TLJH CircleCI Base Image
+========================
+
+Miniconda should be installed in the base CircleCI image for our unit tests.
+Docker CE should be installed in the base CircleCI image for our integration tests.
+
+This image contains both, so we do not have to build it every single time.
+
+Updating the image
+==================
+
+1. Make changes to the ``Dockerfile`` & commit it.
+2. Run ``./build.bash`` from this directory. It'll build, tag & push the image with
+   the hash of the last commit that touched this directory.
+3. Use the new image tag in the ``.circleci/config.yml`` file.

.circleci/base-image/build.bash

@@ -0,0 +1,15 @@
+#!/bin/bash
+set -euo pipefail
+
+# Very simple script to build and push images
+# Should be replaced by chartpress or similar at some point
+# Uses google container image builder for simplicity
+IMAGE="jupyterhub/tljh-circleci-base-image"
+TAG=$(git log -n1 --pretty="%h" .)
+IMAGE_SPEC="${IMAGE}:${TAG}"
+
+
+echo "Building and pushing ${IMAGE_SPEC}"
+docker build -t ${IMAGE_SPEC} .
+docker push ${IMAGE_SPEC}
+echo "Built and pushed ${IMAGE_SPEC}"

.circleci/config.yml

@@ -2,7 +2,7 @@ version: 2
 jobs:
   build:
     docker:
-      - image: continuumio/miniconda3:4.5.4
+      - image: jupyterhub/tljh-circleci-base-image:6fe5372
 
     working_directory: ~/repo
 
@@ -34,29 +34,6 @@ jobs:
         # Run full installer test
       - setup_remote_docker
 
-      - run:
-          #FIXME: Bake this into the base image
-          name: install docker
-          command: |
-            apt-get update
-
-            apt-get install --yes \
-                 apt-transport-https \
-                 ca-certificates \
-                 curl \
-                 gnupg2 \
-                 software-properties-common
-
-            curl -fsSL https://download.docker.com/linux/debian/gpg | apt-key add -
-            add-apt-repository \
-                "deb [arch=amd64] https://download.docker.com/linux/debian \
-                $(lsb_release -cs) \
-                stable"
-
-            apt-get update
-
-            apt-get install --yes docker-ce
-
       - run:
           name: build systemd image
           command: |