afw does not build because there has been a change to the GIL API. They have added a "channel model" argument to the typedef definitions.
Additionally, as a lower priority the test_cache.py test in utils is hanging on macOS with python3.7 and the new boost. Jenkins has no problem with the new boost and python 3.6 so this is seemingly a bad interaction with python3.7. This should not block the update to boost, although python3.7 support was the main motivator for the boost update (and is still a motivation if we wish to investigate the python 3.7 issue).