worker/Dockerfile
FROM r-base:3.6.1
MAINTAINER Franco Bulgarelli
RUN apt-get update && \
apt-get install libxml2 libxml2-dev && \
rm -rf /var/lib/apt/lists/*
RUN R -e "install.packages('remotes'); \
remotes::install_version('xml2', '1.2.2'); \
remotes::install_version('testthat', '2.3.1')"