* Add default license header to files which have no copyright or license header yet.
* yml extension should have been xml...
(cherry picked from commit 1ab2a5f1bc)
* Add dependent lookup plugin.
* Use correct YAML booleans.
* Began complete rewrite.
* Only match start of error msg.
* Improve tests.
* Work around old Jinja2 versions.
* Fix metadata.
* Fix filter name.