sudo: false
language: python
python:
  - "3.5"
  - "3.6"
  - "pypy3"
env:
  - DJANGO="1.11"
  - DJANGO="2.0"
  - DJANGO="2.1"
matrix:
  include:
    - python: 2.7
      env: DJANGO="1.11"
    - python: 3.7
      env: DJANGO="2.0"
      dist: xenial
      sudo: true
    - python: 3.7
      env: DJANGO="2.1"
      dist: xenial
      sudo: true
branches:
  only:
    - master
install:
  - ./.travis_setup
script:
  - tox -- --cov
after_success:
  coveralls

dist: xenial
sudo: false
language: python
python:
  - "3.5"
  - "3.6"
  - "pypy3.5-6.0"
env:
  - DJANGO="1.11"
  - DJANGO="2.0"
  - DJANGO="2.1"
matrix:
  include:
    - python: 2.7
      env: DJANGO="1.11"
    - python: 3.7
      env: DJANGO="2.0"
    - python: 3.7
      env: DJANGO="2.1"
branches:
  only:
    - master
install:
  - ./.travis_setup
script:
  - tox -- --cov
after_success:
  coveralls

Switch to running all tests on Xenial
Switch to running all tests on Xenial

It's officially supported without sudo now, so it makes sense to stop special casing Python 3.7 to it and just run them all.
