version: 2.1
commands:
  commonsteps:
    steps:
      - checkout
      - run: |
          pip install .[dev]
          tox -e py
jobs:
  build_target:
    docker:
      - image: python:3.7
    steps:
      - checkout
      - run: |
          python setup.py sdist
          python setup.py bdist_wheel
          pip install .[dev]
          tox -e py,lint
      - store_artifacts:
          path: dist
          destination: artifacts

  build_latest:
    docker:
      - image: python:latest
    steps:
      - commonsteps

workflows:
  version: 2
  workflow:
    jobs:
      - build_target
      - build_latest

  check_latest:
    triggers:
      - schedule:
          cron: "0 0 * * 0"
          filters:
            branches:
              only: master
    jobs:
      - build_latest

version: 2.1
commands:
  commonsteps:
    steps:
      - checkout
      - run: |
          pip install .[dev]
          tox -e py
jobs:
  build_target:
    docker:
      - image: python:3.8
    steps:
      - checkout
      - run: |
          python setup.py sdist
          python setup.py bdist_wheel
          pip install .[dev]
          tox -e py,lint
      - store_artifacts:
          path: dist
          destination: artifacts

  build_37:
    docker:
      - image: python:3.7
    steps:
      - commonsteps

  build_latest:
    docker:
      - image: python:latest
    steps:
      - commonsteps

workflows:
  version: 2
  workflow:
    jobs:
      - build_37
      - build_target
      - build_latest

  check_latest:
    triggers:
      - schedule:
          cron: "0 0 * * 0"
          filters:
            branches:
              only: master
    jobs:
      - build_latest

Move build target to 3.8, add job for 3.7
Move build target to 3.8, add job for 3.7
