## Steps (Choose relevant, delete irrelevant before submitting)
### All Pull Requests
- [x] Use correct spelling and grammar.
- [ ] Update [RELEASE_NOTES.md](../RELEASE_NOTES.md) if there are noteworthy changes, especially if there are changes to existing APIs.
- [ ] Close/update issues.
- [ ] Check the copyright situation of your changes and sign off your patches (`git commit --signoff`, see [copyright](../CONTRIBUTING.rst#copyright-and-sign-off)).
### Code Changes
- [ ] Run `flake8` to check code style (follow PEP-8 style). `flake8` has issues with parsing Migen/gateware code, ignore as necessary.
- [ ] Test your changes or have someone test them. Mention what was tested and how.
- [ ] Add and check docstrings and comments
- [ ] Check, test, and update the [unittests in /artiq/test/](../artiq/test/) or [gateware simulations in /artiq/gateware/test](../artiq/gateware/test)
- [ ] Split your contribution into logically separate changes (`git rebase --interactive`). Merge/squash/fixup commits that just fix or amend previous commits. Remove unintended changes & cleanup. See [tutorial](https://www.atlassian.com/git/tutorials/rewriting-history/git-rebase).
- [ ] Write short & meaningful commit messages. Review each commit for messages (`git show`). Format: