this is for the experimental build (v1.8.5-20161020-13-gf5ca668 on 2016-10-24', machine='Adafruit Metro M0 with Flash (Experimental) with samd21g18)

boot.py does not load on start and writing to the file system on mac 10.11.6 (usb drive MICROPYTHON) gives an error, but does save (see screenshot).
.................
Traceback (most recent call last):
File "", line 1, in
NameError: name 'help' is not defined
import os
os.uname()
(sysname='samd21', nodename='samd21', release='1.8.5', version='v1.8.5-20161020-13-gf5ca668 on 2016-10-24', machine='Adafruit Metro M0 with Flash (Experimental) with samd21g18')
...............