Fix for #1431753 enables nVidia drivers even if formerly disabled, potentially breaking working systems

[teo1978]

A lot of people, like me, had NVidia drivers installed and disabled since around Ubuntu 12.04, when you could easily choose whether to use them or not. Since they were buggy with some models of NVidia cards, many of us just turned them off.

It wasn't necessary to uninstall them at that time. You would just go to a nice System Settings screen and you would choose Nouveau instead and forget about them. And there was no warning or indication that you were supposed to uninstall them.

Recently, in order to fix #1431753, an automatic update has been released that replaces NVidia drivers 331 with 340.

Unfortunately, it also forcefully reenables them, as now having NVidia drivers installed but disabled is not supported any more (or that'w what I am insistingly told from #1431753).
So, people like me who had NVidia drivers 331 installed and not being used, now have NVidia drivers 340 installed and enabled, and since they are exactly as buggy as version 331 (causing random inability to boot half of the times, and random screen freezes when using the touchpad), this is a major annoyance.

An automatic update that breaks a working system has a bug, no matter what; and this is especially unquestionable if, whatever configuration that causes the system to break with the new update, was not the result of the user's tinkering and touching stuff he wasn't supposed to touch, but was just a configuration that at some point had been supported, and which had been established via the standard user interface provided in earlier versions of the system.

This situation must be fixed without obliging the user to take any particular action.
If that is not possible, then the next update should cause a popup message to be displayed, instructing the user about what to do if in order to (100% safely) disable or uninstall NVidia drivers if he needs to.

[teo1978 (teo8976)]

Another user confirmed the same issue at
https://bugs.launchpad.net/ubuntu/+source/nvidia-graphics-drivers-340-updates/+bug/1431753/comments/97
https://bugs.launchpad.net/ubuntu/+source/nvidia-graphics-drivers-340-updates/+bug/1431753/comments/104

[teo1978 (teo8976)]

From https://bugs.launchpad.net/ubuntu/+source/nvidia-graphics-drivers-340-updates/+bug/1431753/comments/136

> my family and friends switched back to Nouveau via the driver utility
> I have added a screenshot

I may be wrong because the screenshot is in German, but that looks a lot like the utility I used ages ago to switch to NVidia, and then switch back to Nouveau.
Does that now uninstall NVidia drivers when you select Nouveau? (it certainly didn't back when I used it) Because if it doesn't, then Alberto Milone's claims, that having NVidia drivers installed and not used is unsupported, would be bullshit (or the utility would be encouraging the user to do unsupported things which would be a bug).