Configure hawkeye to update license headers

[KushalP]

You can test this with:

hawkeye check --fail-if-unknown

You can update header comments with:

hawkeye format --fail-if-unknown

Ref: https://github.com/korandoru/hawkeye/

[bioball]

By the way, the experience with hawkeye seems a little rough around the edges, because it takes two commits to format?

1. Create or update a file, commit
2. Run hawkeye format, commit

But I think we can go ahead and use it and see how it goes for now.

[KushalP]

By the way, the experience with hawkeye seems a little rough around the edges, because it takes two commits to format?

This is because you're using attrs.git_file_created_year now, which requires git knowing about the file. It may be possible to change the behaviour of hawkeye to use attrs.git_file_created_year or mtime if it's not in git history yet.