sudo: false
# Default python version is 3.6 or later
language: python
cache:
  directories:
    - $HOME/.pip-cache/
env:
  - TOX_ENV=py36
  - TOX_ENV=py36-withlxml
  - TOX_ENV=py37
  - TOX_ENV=py37-withlxml
  - TOX_ENV=py38
  - TOX_ENV=py38-withlxml
  - TOX_ENV=docs
install:
  - pip install --upgrade pip
  - pip install tox
script:
  - tox -e $TOX_ENV
after_script:
  - cat .tox/$TOX_ENV/log/*.log

language: python
  - "3.6"
  - "3.7"
  - "3.8"
install: pip install tox-travis
script: tox

Simplify and improve Travis CI config
Simplify and improve Travis CI config

- specify all target Python 3 versions for testing
- use tox-travis to run the appropriate Tox env for each Python version
- remove extraneous directives.
