Comment 0 for bug 1818748

When trying to work out what the correct input format for installation was (cf. bug 1818746), I discovered that `install --gpgpu` is extremely permissive with what strings it will accept when a version number is given:

```
# The correct invocation (AIUI)
$ ubuntu-drivers install --gpgpu nvidia:410
nvidia-headless-no-dkms-410
...
```

```
# What I was trying
$ ubuntu-drivers install --gpgpu nvidia-driver:410
nvidia-headless-no-dkms-410
...
```

```
# A suffix of nvidia (which also happens to be the name of a free driver)
$ ubuntu-drivers install --gpgpu nv:410
nvidia-headless-no-dkms-410
...
```

```
# No driver name at all!
$ ubuntu-drivers install --gpgpu :410
nvidia-headless-no-dkms-410
...
```

This level of flexibility is actually quite confusing for users, because they don't know what the Right thing to pass in is. Furthermore, it's going to lead to some confusing scripting down the line (consider a case where there's more than one nvidia family of drivers; what would "nv:410" resolve to?)

I think not accepting anything but the actual name ("nvidia") is the right thing to do here (and is the behaviour when a version isn't specified).