Just to put it down on paper, we don't have python2.7 in Bionic. Since python is always supposed to refer to python2, python just fails. obamenu doesn't have python3 compatibility, however, so it fails, too. In order to make this work you have two options:
- get python/python2.7 in Bionic and the proposed patch will work
- use both of the patches the OP provided as the second one provides python3 compatibility
Note that Cosmic has all three, as does Xubuntu Bionic. I would expect that, frankly. That said, I would suggest #1.