Simplify travis config.
language: python
-sudo: required
dist: xenial
os: linux
@@ -30,8 +29,6 @@ matrix:
before_script: TOX_ENV=pylint
- env: ENV=mypy
python: 3.7
- dist: xenial
- sudo: required
before_script: TOX_ENV=mypy
- env: ENV=coverage
python: 3.7
