anchor.diff:  RUN dpkg -i libxaw7_1.0.13-1_amd64.deb
   RUN dpkg -i libxkbfile1_1.0.8-1_amd64.deb
   RUN dpkg -i x11-xkb-utils_7.7+2_amd64.deb
  -RUN dpkg -i xserver-common_1.17.3-2_all.deb
  -RUN dpkg -i xvfb_1.17.3-2_amd64.deb
  +RUN dpkg -i xserver-common_1.18.1-1_all.deb
  +RUN dpkg -i xvfb_1.18.1-1_amd64.deb
   
  -RUN wget http://security.debian.org/debian-security/pool/updates/main/i/iceweasel/iceweasel_38.6.0esr-1~deb8u1_amd64.deb
  -RUN dpkg -i iceweasel_38.6.0esr-1~deb8u1_amd64.deb
  +RUN wget http://security.debian.org/debian-security/pool/updates/main/i/iceweasel/iceweasel_38.6.1esr-1~deb8u1_amd64.deb
  +RUN dpkg -i iceweasel_38.6.1esr-1~deb8u1_amd64.deb
   
   #RUN wget "https://ftp.mozilla.org/pub/firefox/releases/${FF_VERSION}/linux-x86_64/en-US/firefox-44.0.sdk.tar.bz2" \
   #    -O /tmp/firefox.tar.bz2 && \
  
positive.code: COPY xvfb-run /usr/local/bin/
  RUN chmod +x /usr/local/bin/xvfb-run
  
  # cleanup
  RUN apt-get clean
  RUN rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
  
negative.code:         && rm -rf /var/lib/apt/lists/*
  
  #install fake X server
  RUN wget http://ftp.us.debian.org/debian/pool/main/x/xorg-server/xvfb_1.18.1-1_amd64.deb
  RUN wget http://ftp.us.debian.org/debian/pool/main/libx/libxfont/libxfont1_1.5.1-1_amd64.deb
  RUN wget http://ftp.us.debian.org/debian/pool/main/libf/libfontenc/libfontenc1_1.1.2-1+b2_amd64.deb
  RUN wget http://ftp.us.debian.org/debian/pool/main/x/xkeyboard-config/xkb-data_2.12-1_all.deb
  