Switch to python3 base image for deploy too
Switch to python3 base image for deploy too

- Don't install docker.io, we were only using the client
  bits for chartpress. No longer needed
- Python itself comes from the base image now!

berkeley-dsep-infra/datahub,berkeley-dsep-infra/datahub,ryanlovett/datahub,ryanlovett/datahub,berkeley-dsep-infra/datahub,ryanlovett/datahub