This is for sure caused by the python3 installation. I get the same issue on my machine with a local Python 3.9 installation, which I needed since Ubuntu 16.04 only gets 3.5 from aptitude.
> which python
/usr/bin/python
> which python3
/usr/local/bin/python3
> python3 --version
Python 3.9.1
> dpkg -l | grep python
See attached grep.txt
This is for sure caused by the python3 installation. I get the same issue on my machine with a local Python 3.9 installation, which I needed since Ubuntu 16.04 only gets 3.5 from aptitude.
> which python bin/python3
/usr/bin/python
> which python3
/usr/local/
> python3 --version
Python 3.9.1
> dpkg -l | grep python
See attached grep.txt