That’s because python on your system is still linked to Python 3.
Change the link to Python 2 or add the shebang in tegrasign_v3_util.py:
#!/usr/bin/env python2
from __future__ import print_function
#
# Copyright (c) 2018-2023, NVIDIA Corporation. All Rights Reserved.
#
# NVIDIA Corporation and its licensors retain all intellectual property
# and proprietary rights in and to this software, related documentation
# and any modifications thereto. Any use, reproduction, disclosure or
# distribution of this software and related documentation without an express
# license agreement from NVIDIA Corporation is strictly prohibited.
#