Comment 1 for bug 1818746

I'm actually being generous above; a user is much more likely to do:

```
$ ubuntu-drivers install nvidia-driver-410
usage: ubuntu-drivers [-h] [--package-list PATH]
                      [--gpgpu [driver[:version][,driver[:version]]]]
                      [<command>]
ubuntu-drivers: error: unrecognized arguments: nvidia-driver-410
```

which is an even worse error message. So `list`s output should probably also guide the user towards the correct installation method.