[BUILD][python] dist target fails in ubertool docker

+ cd lang/py
+ ./build.sh dist
The virtual environment was not created successfully because ensurepip is not
available.  On Debian/Ubuntu systems, you need to install the python3-venv
package using the following command.    apt-get install python3-venvYou may need to use sudo with that command.  After installing the python3-venv
package, recreate your virtual environment.Failing command: ['/tmp/tmp.4RQC7RDTxc/bin/python3', '-Im', 'ensurepip', '--upgrade', '--default-pip']