anchor.diff:      tk-dev \
       xz-dev \
       zlib-dev \
  +
   # add build deps before removing fetch deps in case there's overlap
     && apk del .fetch-deps \
     \
  
positive.code:   && rm python.tar.xz \
    \
    && apk add --no-cache --virtual .build-deps  \
      bzip2-dev \
      coreutils \
      dpkg-dev dpkg \
  
negative.code: 
  # install ca-certificates so that HTTPS works consistently
  # other runtime dependencies for Python are installed later
  RUN apk update && \
      apk add --no-cache \
          ca-certificates \
          libressl \
          pcre \
          zlib
  
  ENV GPG_KEY 0D96DF4D4110E5C43FBFB17F2D347EA6AA65421D
  ENV PYTHON_VERSION 3.6.9
  