language: python
sudo: false
python: 3.7
env:
    - TOX_ENV=py37
    - TOX_ENV=py37-flake8
install:
    - pip install tox
script:
    - tox -e $TOX_ENV

dist: xenial
language: python
sudo: false
python: 3.7
env:
    - TOX_ENV=py37
    - TOX_ENV=py36
    - TOX_ENV=py37-flake8
install:
    - pip install tox
script:
    - tox -e $TOX_ENV

Add py36 to testing env and xenial distribution.
Add py36 to testing env and xenial distribution.
