Cannot use gnome-app-install with an addon CD

[Thomas Fogwill]

With the current version of gnome-app-install in the karmic beta (0.5.60.1ubuntu1), it is not possible to use the --addon-cd option. Instead of displaying the contents of the archive on the addon CD, the contents of the apt cache are shown (i.e. as though --addon-cd were not given as option).

Steps to reproduce:
 1. insert an addon CD (or loop mount its ISO)
 2. click on the "start addon installer" button if the autorun dialog appears
     OR
     run gnome-app-install --addon-cd=<path to mountpoint of the CD>

Expected behaviour:
gnome-app-install shows the contents of the addon cd (as per the files in app-install/)

Actual behaviour:
The full contents of the apt cache are shown (same as what is shown if gnome-app-install is run without --addon-cd). The packages on the addon CD are not available at all.

To test/verify, an ISO can be downloaded from here: http://scubuntu.meraka.org.za/~tfogwill/scubuntu-test-cdimages/karmic/
or the edubuntu 9.04 addon CD can be used.

[Thomas Fogwill (thomas-fogwill)]

The problem seems to be caused by three different problems in the code:

1. The addonCD method in PackagingBackendApt.py does not return anything, so AppInstallApp.py thinks the CD doesn't exist
2. AppInstallApp.py needs to set the value of local variable cd_desktopdir
3. Menu.py needs to initialise cacheLoaded (it is never initialised if cachedir is None)

The attached debdiff fixes these 3 issues, and fixes the bug.