More minimal, faster build

* Use setuptools to get modern pip (debian packaged pip stops
  working after requests gets updated)
* Don't use wget to fetch tini, use Python!

(c) Copyright IBM Corp. 2016

minimal-kernel/Dockerfile

@@ -8,20 +8,15 @@ USER root
 # Install all OS dependencies for fully functional notebook server
 ENV DEBIAN_FRONTEND noninteractive
 RUN apt-get update && apt-get install -yq --no-install-recommends \
-    python3-pip \
     python3-zmq \
     && apt-get clean
 
 # Install Tini
-RUN apt-get update && \
-    apt-get install -yq --no-install-recommends wget && \
-    wget --quiet https://github.com/krallin/tini/releases/download/v0.6.0/tini && \
+RUN python3 -c 'from urllib.request import urlretrieve; \
+urlretrieve("https://github.com/krallin/tini/releases/download/v0.6.0/tini", "tini")' && \
     echo "d5ed732199c36a1189320e6c4859f0169e950692f451c03e7854243b95f4234b *tini" | sha256sum -c - && \
     mv tini /usr/local/bin/tini && \
-    chmod +x /usr/local/bin/tini && \
-    apt-get remove --purge -y wget && \
-    apt-get autoremove -y && \
-    apt-get clean
+    chmod +x /usr/local/bin/tini
 
 # Configure environment
 ENV KG_USER jovyan
@@ -30,11 +25,18 @@ ENV KG_UID 1000
 # Create jovyan user with UID=1000
 RUN useradd -m -s /bin/bash -N -u $KG_UID $KG_USER
 
-# Install Kernel Gateway
+# Install modern pip then kernel gateway
 RUN apt-get update && \
-    apt-get install -yq --no-install-recommends build-essential python3-dev && \
-    pip3 install jupyter_kernel_gateway==0.2.0 && \
-    apt-get remove --purge -y build-essential python3-dev && \
+    apt-get install -yq --no-install-recommends \
+        build-essential \
+        python3-dev \
+        python3-setuptools && \
+    easy_install3 pip && \
+    pip install jupyter_kernel_gateway==0.2.0 && \
+    apt-get remove --purge -y \
+        build-essential \
+        python3-dev \
+        python3-setuptools && \
     apt-get autoremove -y && \
     apt-get clean