py3: port ext-phase-report.py extension The custom module importer doesn't run on Python files in the tests directory. So we need the source to be compatible with both Python 2 and 3. Differential Revision: https://phab.mercurial-scm.org/D2145

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

py3: use bytes() to cast context instances __str__ and __bytes__ are both implemented on context types. However, __str__ behaves differently on Python 2 and 3. Differential Revision: https://phab.mercurial-scm.org/D2143