fn boxed<'a, I: Iterator<Item = Error> + 'a>(iter: I) -> Box<dyn Iterator<Item = Error> + 'a> {
pub(crate) fn check_content_errors(&self, path: &Path) -> impl Iterator<Item = Error> + '_ {
// iOS: https://developer.apple.com/library/archive/documentation/FileManagement/Conceptual/FileSystemProgrammingGuide/FileSystemOverview/FileSystemOverview.html