In all three cases of Ubuntu 18.04 and later 19.10 and also in Ubuntu 20.04 I solved this bug by clicking:
System → Synaptic Package Manager
Search for python-is
Uninstall python-is-python2
install python-is-python3
Screenshot attached.
It appears that HPLIP needs Python 3, but Ubuntu defaults to the deprecated Python 2. It appears that HP needs to specify the python version it needs, or Ubuntu needs to not default to the deprecated version. Both corrections might save a lot of problems.
In all three cases of Ubuntu 18.04 and later 19.10 and also in Ubuntu 20.04 I solved this bug by clicking:
System → Synaptic Package Manager
Search for python-is
Uninstall python-is-python2
install python-is-python3
Screenshot attached.
It appears that HPLIP needs Python 3, but Ubuntu defaults to the deprecated Python 2. It appears that HP needs to specify the python version it needs, or Ubuntu needs to not default to the deprecated version. Both corrections might save a lot of problems.
Hope this helps.