make jupyterhub a build arg

and verify that it's installed in tests

repo2docker/detectors.py

@@ -65,6 +65,9 @@ RUN apt-get update && \
     rm -rf /var/lib/apt/lists/*
 {% endif -%}
 
+# make JUPYTERHUB_VERSION a build argument
+ARG JUPYTERHUB_VERSION=0.7.2
+
 EXPOSE 8888
 
 {% if env -%}
@@ -136,6 +139,16 @@ class BuildPack(LoggingConfigurable):
     and there are *some* general guarantees of ordering.
 
     """
+
+    jupyterhub_version = Unicode(
+        '0.7.2',
+        config=True,
+        help="""JupyterHub version to install.
+
+        In general, the JupyterHub version in the image
+        and the Hub itself should have the same version number.
+        """
+    )
     packages = Set(
         set(),
         help="""
@@ -392,7 +405,10 @@ class BuildPack(LoggingConfigurable):
                 fileobj=tarf,
                 tag=image_spec,
                 custom_context=True,
-                decode=True
+                buildargs={
+                    'JUPYTERHUB_VERSION': self.jupyterhub_version,
+                },
+                decode=True,
         ):
             yield line
 
@@ -481,7 +497,7 @@ class PythonBuildPack(BuildPack):
             r"""
             pip install --no-cache-dir \
                 notebook==5.0.0 \
-                jupyterhub==0.7.2 \
+                jupyterhub==${JUPYTERHUB_VERSION} \
                 ipywidgets==6.0.0 \
                 jupyterlab==0.24.1 && \
             jupyter nbextension enable --py widgetsnbextension --sys-prefix && \
@@ -704,7 +720,10 @@ class DockerBuildPack(BuildPack):
         for line in client.build(
                 path=os.getcwd(),
                 tag=image_spec,
-                decode=True
+                buildargs={
+                    'JUPYTERHUB_VERSION': self.jupyterhub_version,
+                },
+                decode=True,
         ):
             yield line
 
@@ -719,10 +738,11 @@ class LegacyBinderDockerBuildPack(DockerBuildPack):
     USER main
     WORKDIR /home/main/notebooks
     ENV PATH /home/main/anaconda2/envs/python3/bin:$PATH
-    RUN conda install -n python3 notebook==5.0.0 ipykernel==4.6.0 && \
-        pip install jupyterhub==0.7.2 && \
-        conda remove -n python3 nb_conda_kernels && \
-        conda install -n root ipykernel==4.6.0 && \
+    ARG JUPYTERHUB_VERSION
+    RUN conda install -yq -n python3 notebook==5.0.0 ipykernel==4.6.0 && \
+        pip install --no-cache-dir jupyterhub==${JUPYTERHUB_VERSION} && \
+        conda remove -yq -n python3 nb_conda_kernels && \
+        conda install -yq -n root ipykernel==4.6.0 && \
         /home/main/anaconda2/envs/python3/bin/ipython kernel install --sys-prefix && \
         /home/main/anaconda2/bin/ipython kernel install --prefix=/home/main/anaconda2/envs/python3 && \
         /home/main/anaconda2/bin/ipython kernel install --sys-prefix

repo2docker/files/conda/environment.yml

@@ -5,5 +5,3 @@ dependencies:
   - ipykernel==4.6.0
   - ipywidgets==6.0.0
   - jupyterlab==0.22.1
-  - pip:
-    - jupyterhub==0.7.2

repo2docker/files/conda/install-miniconda.bash

@@ -30,6 +30,7 @@ ${CONDA_DIR}/bin/conda config --system --set update_dependencies false
 ${CONDA_DIR}/bin/conda config --system --set show_channel_urls true
 
 ${CONDA_DIR}/bin/conda env update -n root -f /tmp/environment.yml
+${CONDA_DIR}/bin/pip install --no-cache-dir jupyterhub==${JUPYTERHUB_VERSION}
 # Clean things out!
 ${CONDA_DIR}/bin/conda clean -tipsy
 

tests/dockerfile/jupyter-stack/Dockerfile

@@ -1,4 +1,7 @@
 FROM jupyter/base-notebook:b4dd11e16ae4
 
+ARG JUPYTERHUB_VERSION
+RUN pip install jupyterhub==$JUPYTERHUB_VERSION
+
 RUN pip install there
 ADD verify verify

tests/dockerfile/jupyter-stack/verify

@@ -1,7 +1,9 @@
 #!/usr/bin/env python
+import os
 import sys
 
 assert sys.version_info[:2] == (3, 6)
 
 import jupyter
+import jupyterhub
 import there

tests/dockerfile/legacy/verify

@@ -1,6 +1,8 @@
 #!/usr/bin/env python
+import os
 import sys
 
-assert sys.version_info[:2] == (2, 7)
+assert sys.version_info[:2] == (3, 5), sys.version
 
 import jupyter
+import jupyterhub

tests/dockerfile/simple/Dockerfile

@@ -1,4 +1,7 @@
-FROM alpine:3.5
+FROM python:3.5
+
+ARG JUPYTERHUB_VERSION
+RUN pip3 install jupyterhub==$JUPYTERHUB_VERSION
 
 ENTRYPOINT "/bin/sh"