anchor.diff: -FROM       ubuntu:18.04
  +FROM       ubuntu:20.04
   
   RUN mkdir /dreal4
   COPY . /dreal4
  
positive.code: # Install prerequisites.
  ARG DEBIAN_FRONTEND=noninteractive
  RUN apt-get update \
        && yes "Y" | /dreal4/setup/ubuntu/18.04/install_prereqs.sh \
        && apt-get install -y --no-install-recommends apt-utils python3-dev python3-wheel python3-setuptools python3-pip python-zipstream \
        && rm -rf /var/lib/apt/lists/* \
        && apt-get clean all \
  # Build dReal4
  
negative.code:       && tar xfz bazel-bin/archive.tar.gz --strip-components 4 -C /usr \
  # Install Python3 Binding
        && python3 setup.py bdist_wheel \
        && pip3 install ./dist/dreal-*-cp38-none-manylinux1_x86_64.whl \
        && bazel clean --expunge \
  # Clean up
        && cd / \
        && rm -rf dreal4 \
        && rm -rf /root/.cache/bazel \
        && rm -rf /var/lib/apt/lists/* \
        && apt-get remove -y bazel bison flex g++ wget \
        && apt-get autoclean -y \
        && apt-get autoremove -y
  