Hi all,
Flake8 released a new version recently, causing our test suite to break on travis and appveyor, where we install the latest version of flake8 during setup for the test run.
I've issued a pull request which should fix the travis and appveyor tests. It would be nice to get this in quickly to stabilize our test suite.
https://github.com/yt-project/yt/pull/1592
Thanks for your attention,
Nathan