It can be really easy to introduce subtle bugs in the the evergreen.yml file (See SERVER-38822) as an example. Using a yaml linter could catch some of these issues. We should create an evergreen task to run one and as part of a required builder.

This one https://github.com/adrienverge/yamllint seems to work and can be installed as a pip module. We would want to run it in relaxed mode.

yamllint -d relaxed etc/evergreen.yml