Fix Travis CI config validation warnings
MODIFY
.travis.yml
.travis.yml
language: python
-sudo: false
-stage: test
+os: linux
dist: xenial
before_install:
@@ -29,7 +28,7 @@ env:
- PYPI_USERNAME=urllib3
# PYPI_PASSWORD is set in Travis control panel.
-matrix:
+jobs:
include:
# Lint & documentation.
- python: 3.6

Fix Travis CI config validation warnings