anchor.diff:  
   COPY . /synapse
   
  -RUN apk add --no-cache --virtual .nacl_deps \
  +RUN apk add --no-cache --virtual .build_deps \
           build-base \
           libffi-dev \
           libjpeg-turbo-dev \
  
positive.code:         libxslt-dev \
          linux-headers \
          postgresql-dev \
          su-exec \
          zlib-dev \
     
  # A wheel cache may be provided in ./cache for faster build
   && cd /synapse \
   && pip install --upgrade \
          lxml \
          pip \
  
negative.code:         setup.cfg \
          setup.py \
          synapse \
   && apk del .build_deps
   
  VOLUME ["/data"]
  
  