Dockerfile to build apache superset (0.29.0rc7) on a docker container. Superset is setup with a celery backend to process sqlab asyncronously

To change superset configs, update the superset config file

docker build -t docker-superset .

Use the example docker compose file.

As per the rc, the version of cryptography is incompatible. So needed to list out the requirements from the github repo, this can be removed once the release version is changed.