The title basically says it all. I get:
Traceback (most recent call last):
File "rc.py", line 8, in
copter.set_wp(1, 1, 50.9103311, -10.5349744, 0, 10, 0, 0, 0)
File "MSP.py", line 194, in set_wp
payload += int(lon * 10000000).to_bytes(4, byteorder='little')#lon
OverflowError: can't convert negative int to unsigned