In Windows, using CopyFileExW and CreateDirectoryExW (with a template directory, for copytree) doesn't agree with how shutil implements copying with separate copyfile and copymode/copystat functions. We'd have to extend copyfile() to support alternate data streams, and we'd have to extend copystat() to support file attributes, extended attributes, and security-resource attributes. Or we'd have to abandon consistency between copy2 and copyfile+copystat.