anchor.diff:  # Install dependencies.
   RUN apt-get update \
     && apt-get install -y --no-install-recommends \
  +    apt-transport-https \
       build-essential \
       bzip2 \
       ca-certificates \
  +    curl \
       git \
       libbz2-dev \
       libreadline-dev \
       libsqlite3-dev \
       libssl-dev \
  +    software-properties-common \
       ssh \
  +    sudo \
       tcl \
       tcl-dev \
       tk \
  
positive.code:   virtualenv
  
  # Install docker
  RUN apt-get update \
    && apt-get install -y \
       apt-transport-https \
       ca-certificates \
       curl \
       software-properties-common \
       sudo
  
  RUN curl -fsSL https://download.docker.com/linux/ubuntu/gpg | sudo apt-key add -
  
  RUN add-apt-repository \
  
negative.code:    $(lsb_release -cs) \
     stable"
  
  RUN apt-get update \
    && apt-get install -y --no-install-recommends \
      docker-ce \
    && apt-get clean autoclean \
    && apt-get autoremove -y \
    && rm -rf /var/lib/apt/lists/* \
    && rm -f /var/cache/apt/archives/*.deb
  
  CMD ["python3.6"]
  