anchor.diff:  
   # Not essential, but wise to set the lang
   # Note: Users with other languages should set this in their derivative image
  -RUN apt-get update && apt-get install -y language-pack-en && \
  -    apt-get clean
  +RUN apt-get update && apt-get install -y language-pack-en 
   ENV LANGUAGE en_GB.UTF-8
   ENV LANG en_GB.UTF-8
   ENV LC_ALL en_GB.UTF-8
  
positive.code: RUN dpkg-reconfigure locales
  
  # Python binary dependencies, developer tools
  RUN apt-get update && apt-get install -y -q \
      build-essential \
      make \
      gcc \
  
negative.code: # install jupyterhub
  ADD requirements.txt /tmp/requirements.txt
  RUN pip3 install -r /tmp/requirements.txt
  WORKDIR /srv/
  RUN git clone https://github.com/edinburghlivinglab/jupyterhub.git
  WORKDIR /srv/jupyterhub/
  RUN pip3 install .
  
  WORKDIR /srv/jupyterhub/
  