anchor.diff:  # Install Google Chrome
   RUN wget -q -O - https://dl-ssl.google.com/linux/linux_signing_key.pub | apt-key add -
   RUN echo "deb http://dl.google.com/linux/chrome/deb/ stable main" >> /etc/apt/sources.list.d/google.list
  -RUN apt-get update -yy && apt-get install -yy google-chrome-stable
  +RUN apt-get update -q -yy && apt-get install -yy google-chrome-stable
   RUN google-chrome --version
   
   # Install node.js; use most recent version to have access to latest features
   WORKDIR /opt
  -RUN wget https://nodejs.org/dist/v6.2.0/$NODE_ARCHIVE && \
  +RUN wget -q https://nodejs.org/dist/v6.2.0/$NODE_ARCHIVE && \
       tar xJf $NODE_ARCHIVE && \
       ln -s /opt/$NODE_DIR /opt/node && \
       rm $NODE_ARCHIVE
  
positive.code: 
  # Ubuntu's python-pip throws exception with requests lib
  # see https://bugs.launchpad.net/ubuntu/+source/python-pip/+bug/1306991
  RUN wget https://bootstrap.pypa.io/get-pip.py && \
      python get-pip.py && \
      rm get-pip.py
  
  
negative.code: ENV NODE_ARCHIVE=$NODE_DIR.tar.xz
  ENV PATH=/opt/node/bin:$PATH
  
  RUN apt-get -q -y update && apt-get install -y \
          firefox \
          gcc \
          libyaml-dev \
  