anchor.diff:  ARG PYTHON_IMAGE
   FROM ${PYTHON_IMAGE}
   
  -RUN apt-get update && apt-get -y --no-install-recommends install \
  +RUN apt-get -qq update && apt-get -qq -y --no-install-recommends install \
                                                               ca-certificates \
                                                               curl \
                                                               netcat \
  
positive.code:                             hkp://keyserver.ubuntu.com:80 \
                              pgp.mit.edu) ; do gpg --no-tty --keyserver "$server" --recv-keys B42F6819007F00F88E364FD4036A9C25BF357DD4 && s=0 && break || s=$?; done; (exit $s)
  
  RUN curl -o /usr/local/bin/gosu -SL "https://github.com/tianon/gosu/releases/download/1.10/gosu-$(dpkg --print-architecture)" \
      && curl -o /usr/local/bin/gosu.asc -SL "https://github.com/tianon/gosu/releases/download/1.10/gosu-$(dpkg --print-architecture).asc" \
      && gpg --verify /usr/local/bin/gosu.asc \
      && rm /usr/local/bin/gosu.asc \
      && chmod +x /usr/local/bin/gosu
  
negative.code: RUN if command -v pypy3; then ln -s $(command -v pypy3) /usr/local/bin/python; elif command -v pypy; then ln -s $(command -v pypy) /usr/local/bin/python; fi
  
  # pre-install base requirements
  RUN python -m pip install --progress-bar off -U pip && pip install --progress-bar off -r /requirements-base.txt
  
  RUN chmod +x /usr/local/bin/entrypoint.sh
  
  