py3: more robustly cast UUID to bytes The UUID type only has __str__ implemented. So we need to cast to bytes on Python 3. We need an actual bytes instance here (bytestr won't do) because the re.escape() later iterates over characters and characters need to behave like ints, not bytes instances of length 1. Differential Revision: https://phab.mercurial-scm.org/D2144