See #9815 (comment)

With the following snippet, you can use Python 3.7 in your builds:

language: python
python: 3.7
dist: xenial
sudo: true

Thanks!

I'm working on a project that needs to be tested on all versions of python, and when I do this, 2.6, 3.3, and 3.4 fail, but it does allow 3.7 to work.

sudo: false
language: python
dist: "xenial"
sudo: true
python:
  - "2.6"
  - "2.7"
  - "3.3"
  - "3.4"
  - "3.5"
  - "3.6"
  - "3.7"
install:
 - python setup.py install
 - pip install -r test_reqs.txt

Is there a way to tell travis to use xenial for python 3.7, but trusty on the other versions?

Nevermind - the travis.yml here answers my question: #9815

sudo: true is not needed anymore. Travis CI is deprecating that option and moving back to a VM-only infrastructure (no more containers with sudo: false).