allow uploader script to read OTP and SN from the v4 boards
and display the info to the user/s, so they can see for themselves
what the serial number of their PX4/Pixhawk is.
fix attribute eror in some instances.
AttributeError: 'uploader' object has no attribute 'otp'
pull in one remaining recent commit from the PX4 repo.
this commit taken from https://github.com/PX4/Firmware/commit/dcfd5bdbe7d999db70e3d4e3e08320e03cc3840a
Uploader: Python 3 support
Merge pull request #9 from PX4/uploader_fix_python3

Uploader fix OTP with python3 support