anchor.diff:      && rm -rf /var/lib/apt/lists/*
   
   #  install the packages necessary to build Python source:
  -RUN apt update && apt install -y build-essential zlib1g-dev libncurses5-dev libgdbm-dev \
  +RUN apt update && apt install -y --no-install-recommends build-essential zlib1g-dev libncurses5-dev libgdbm-dev \
       libnss3-dev libssl-dev libreadline-dev libffi-dev libbz2-dev \
       libncursesw5-dev libsqlite3-dev tk-dev libc6-dev ca-certificates \
       && apt-get clean \
  
positive.code: # install dev dependencies for react, javascript development. These are not needed at runtime.
  RUN apt-get update \
      && curl -sL https://deb.nodesource.com/setup_8.x | bash - \
      && apt-get install -y \
          nodejs \
      && apt-get clean \
      && rm -rf /var/lib/apt/lists/*
  
  # install database clients for debugging (https://www.postgresql.org/download/linux/debian/)
  RUN echo "deb http://apt.postgresql.org/pub/repos/apt $(lsb_release -cs)-pgdg main" > /etc/apt/sources.list.d/pgdg.list \
      && wget --quiet -O - https://www.postgresql.org/media/keys/ACCC4CF8.asc | apt-key add - \
      && apt-get update && apt-get install -y \
          postgresql \
          postgresql-client \
          libpq-dev \
  
negative.code:     && apt-get clean \
      && rm -rf /var/lib/apt/lists/*
  
  RUN curl -L0 https://raw.github.com/miyagawa/cpanminus/master/cpanm -o /usr/bin/cpanm \
      && chmod +x /usr/bin/cpanm \
      && cpanm --notest \
          Cairo \
  