The ‘3to2’ refer below:
Install ‘3to2’ package in your python 3 env.
Note! Attention! Please!
If you installed python2 and python3.
pip3 install 3to2
pip default using version is python2.
pip3 is using for python3.
pip3 install 3to2 will be recommended, while your system have to version of python 2 and 3.
Because 3to2 only run in python version > 3.x
Because of this reason, I met the some frustation. So, that’s all.