prow/repoowners/repoowners.go
func (o *RepoOwners) RequiredReviewers(path string) sets.String {
	return o.entriesForFile(path, o.requiredReviewers, false)
}
func (o *RepoOwners) RequiredReviewers(path string) sets.String {
	return o.entriesForFile(path, o.requiredReviewers, false)
}
// RequiredReviewers returns ALL of the users who are required_reviewers for the
// requested file (including required_reviewers in parent dirs' OWNERS).
// If pkg/OWNERS has user1 and pkg/util/OWNERS has user2 this
// will return both user1 and user2 for the path pkg/util/sets/file.go