anchor.diff:    ; do \
       keyserver_ok=""; \
       for keyserver in ${keyservers}; do \
  -      gpg --keyserver ${keyserver} --recv-keys "$key"; >/dev/null 2>&1 && keyserver_ok="ok" && break;\
  +      gpg --batch --keyserver ${keyserver} --recv-keys "$key"; >/dev/null 2>&1 && keyserver_ok="ok" && break;\
       done; \
       if [ -z "$keyserver_ok" ]; then echo "No valid response from keyservers"; exit 1; fi; \
     done
  
positive.code: 
  # gpg keys listed at https://github.com/nodejs/node#release-team
  RUN set -ex \
    && keyservers="hkp://p80.pool.sks-keyservers.net:80 ha.pool.sks-keyservers.net hkps.pool.sks-keyservers.net pool.sks-keyservers.net keyserver.ubuntu.com" \
    && for key in \
      94AE36675C464D64BAFA68DD7434390BDBE9B9C5 \
      FD3A5288F042B6850C66B31F09FE44734EB7990E \
  
negative.code: FROM openjdk:8-stretch
  
  # used to download sources, executables
  RUN apt-get update \
  