'python-gtk2' error
'python-gtk2' error when running your install on Ubuntu 20.04. because Ubuntu no longer has 'pip' by default.
It goes further than that. 20.04 does not support Python 2.7. It comes with Python 3. PyGTK, however is deprecated and there's no version for Python 3 any more.
Here's some info on porting to the successor: https://wiki.gnome.org/action/show/Projects/PyGObject/IntrospectionPorting https://python-gtk-3-tutorial.readthedocs.io/en/latest/index.html
In 2022, error the same, "Failed to import GTK: No module named 'gtk'". Version is 0.6.4, marked as latest release, trying under Linux Mint 20.3. I see a many forks of this project, maybe, anyone made it runnable under Python 3?