Based on a CircleCI image, but adds QT4 and FFPMEG and nodejs/yarn.
Current Image: esparklearning/ruby-ci:2.6.3
To build a new image:
We base our versions on Circle CI's Ruby images. Update the Dockerfile accordingly and, once it builds, run:
docker build -t ${VERSION} .
docker tag ${VERSION} esparklearning/ruby-ci/${VERSION}
docker push esparklearning/ruby-ci:${VERSION}