Update pydfu.py to match with the version from openmv. I just updated the openmv version to work with both of the PyUSB 1.0.0.b1 and 1.0.0.b2 See: https://github.com/walac/pyusb/blob/master/ReleaseNotes.rst
You can do: make USE_PYDFU=1 deploy to use pydfu.py