Download images from Dockerhub.
For now, we have following images:
- python-poetry:3.8, python-poetry:latest
- python-poetry:3.7
- python-poetry:3.6
- python-poetry:3.8-slim, python-poetry:slim
- python-poetry:3.7-slim
- python-poetry:3.6-slim
- python-poetry:3.8-alpine, python-poetry:alpine
- python-poetry-alpine:3.7
- python-poetry-alpine:3.6