anchor.diff:      pip install 'pip<10' && \
       pip install -U setuptools
   
  +ARG ROS_DISTRO
   RUN cd ~ && \
       mkdir -p ros/${ROS_DISTRO}/src && \
       cd ros/${ROS_DISTRO}/src && \
  
positive.code: ARG UBUNTU_VERSION
  FROM osrf/ros:${ROS_DISTRO}-desktop-${UBUNTU_VERSION}
  
  ARG ROS_DISTRO
  ARG TESTING
  RUN echo "deb http://packages.ros.org/ros-testing/ubuntu $(lsb_release -sc) main" > /etc/apt/sources.list.d/ros-latest.list
  
  RUN apt-get update && apt-get install -y wget git
  
negative.code: # /opt/ros/${ROS_DISTRO}/share can be changed after rosdep install, so we run it 3 times.
  RUN for i in $(seq 3); do rosdep install --rosdistro ${ROS_DISTRO} -r -y -i --from-paths /opt/ros/${ROS_DISTRO}/share ~/ros/${ROS_DISTRO}/src; done
  
  ARG TESTING
  RUN if [ ${TESTING} = "true" ] ; then \
        rm -rf ~/ros; \
      else \
  