When package configuration question is asked, default choice in GUI is incorrect and other options don't work

[Pierre Equoy]

Ubuntu version used: 14.04.2

(If this is not the right place to raise this issue, please let me know where I should put it)

After raising issue lp:1457353, I realized the default choice for the GUI version was different than the default choice for the CLI version.

Steps to reproduce:

CLI:
1. Install a fresh Ubuntu 14.04.2
2. Modify file /etc/default/grub (for instance, commenting a line or adding a few comments), save and run sudo update-grub2.
3. In a terminal, run:
    sudo apt-get update && sudo apt-get dist-upgrade
4. When package grub-pc is being configured, you should see a screen similar to attachment grub-cli-choice.png. Please note the default choice is the second line of the list: "keep the local version currently installed"

GUI:
1. Install a fresh Ubuntu 14.04.2
2. Modify file /etc/default/grub (for instance, commenting a line or adding a few comments), save and run sudo update-grub2.
3. Install package libgtk2-perl: sudo apt-get install libgtk2-perl (to avoid issue explained in lp:1457353)
4. Restart the computer and start Software Updater to install the latest versions of packages.
5. When grub-pc is being configured, you should see a screen similar to attachment grub-gui-choice.png. Please note the selected choice is the first of the list: "install the package maintainer's version"

CLI and GUI differs on how the configuration file is updated!

In addition to this, it looks like other options cannot be run properly in GUI mode. For instance, if you select "show the differences between the versions" in CLI mode, a new window shows a diff-style information with the differences. If you select the same option with the GUI and press Forward, nothing is shown and the software update continue happily... (so I actually don't know what choice is made and if the file is actually kept or updated!)