anchor.diff:    sudo \
     unzip \
     wget \
  -  gnupg2 \ 
  +  gnupg2 \
  +  apt-utils \
     software-properties-common \
     bzr
   
  
positive.code:     zlib1g-dev \
      libpython2.7 \
      tzdata \
      pkg-config \
      && rm -r /var/lib/apt/lists/*
  
  # pub   4096R/ED3D1561 2019-03-22 [expires: 2021-03-21]
  #       Key fingerprint = A62A E125 BBBF BB96 A6E0  42EC 925C C1CC ED3D 1561
  # uid                  Swift 5.x Release Signing Key <swift-infrastructure@swift.org
  ARG SWIFT_SIGNING_KEY=A62AE125BBBFBB96A6E042EC925CC1CCED3D1561
  ARG SWIFT_PLATFORM=ubuntu16.04
  ARG SWIFT_BRANCH=swift-5.3.3-release
  ARG SWIFT_VERSION=swift-5.3.3-RELEASE
  ARG SWIFT_WEBROOT=https://swift.org/builds/
  
negative.code: ENV LANGUAGE=en_US:en
  ENV LC_ALL=en_US.UTF-8
  
  # install Cargo
  RUN curl https://sh.rustup.rs -sSf | bash -ls -- -y --profile minimal
  
  #install rvm
  RUN apt-add-repository -y ppa:rael-gc/rvm && \
      apt update && apt install -y rvm && \
      /usr/share/rvm/bin/rvm install --default $RUBY_VERSION
  
  # install bundler
  RUN bash -lc "gem update --system && gem install bundler"
  
  #install mix
  RUN wget https://packages.erlang-solutions.com/erlang-solutions_${MIX_VERSION}_all.deb && \
  