Add underscore guideline to CONTRIBUTING.md
@@ -210,6 +210,8 @@ General guidelines for pull requests (PRs):
* Larger changes should be broken down into smaller components and integrated
separately.
* Bug fixes should be submitted in separate PRs.
+* Use underscores for all Python (*.py) files as per [PEP8](https://www.python.org/dev/peps/pep-0008/),
+ not hyphens. Directory names should also use underscores instead of hyphens.
* Describe what your PR changes and *why* this is a good thing. Be as specific as you
can. The PR description is how we keep track of the changes made to the project over
time.
