[SOLVED]
Looking at the github
https://github.com/groupgets/pylepton. The master branch was updated for python3 but only for Lepton2. The branch Lepton3-dev seems like it was created to run Lepton3 with python3 but got the error in the file Lepton3.py
Change line 8 and 11 in Lepton3.py by adding a "." and include bracket "()" in all the print statements should fix the problem
ln 8: from ioctl_numbers import _IOR, _IOW
--> from .ioctl_numbers import _IOR, _IOW
ln 11: from Lepton import Lepton
--> from .Lepton import Lepton