Change from system Python to environment python3. For Ubuntu 20.04, only `python3` is available and there's no `python`. So at least `python3` is consistent with Python virtual env, Ubuntu and anaconda.
Change from system Python to environment python3. For Ubuntu 20.04, only `python3` is available and there's no `python`. So at least `python3` is consistent with Python virtual env, Ubuntu and anaconda.