In this thread somone got the same error with th nc-who script, and I’d say they probably on Ubuntu have the universe repo disbaled for some reason.
In Debian the ansifilter package is in main, which of course always needs to be enabled to be able to use Debian, but in Ubuntu it’s in universe, which should also be enabled by default, but who knows, maybe it’s been disabled by the user, either intentionally or unintentionally when messing with the sources.list. Or maybe there are some Ubuntu based distros out there where it’s disabled for some reason… 
@Vadim If you are on Ubuntu, try the following and then run the script again:
sudo add-apt-repository universe