Problème de misa à jour Ubuntu

comment je dois faire pour virer ça?

sudo apt-add-repository --remove ppa:<nom_du_dépôt>

ça ne marche pas, voilà le résultat:
desktop:~$ sudo apt-add-repository --remove ppa:crebs

You are about to add the following PPA to your system:
Create Background Slideshow
Stable releases for Create Background Slideshow
More info: https://launchpad.net/~crebs/+archive/ppa
Press [ENTER] to continue or ctrl-c to cancel adding it

Error: 'deb http://ppa.launchpad.net/crebs/ppa/ubuntu oneiric main' doesn't exist in a sourcelist file

Qu'y a-t-il dans ton sources.list ?

cat -n /etc/apt/sources.list

voilà ce que donne la commande:
1 # deb cdrom:[Ubuntu 11.10 _Oneiric Ocelot_ - Release amd64 (20111012)]/ dists/oneiric/main/binary-i386/
2
3 # deb cdrom:[Ubuntu 11.10 _Oneiric Ocelot_ - Release amd64 (20111012)]/ oneiric main restricted
4
5 # See http://help.ubuntu.com/community/UpgradeNotes for how to upgrade to
6 # newer versions of the distribution.
7 deb http://fr.archive.ubuntu.com/ubuntu/ oneiric main restricted
8 deb-src http://fr.archive.ubuntu.com/ubuntu/ oneiric main restricted
9
10 ## Major bug fix updates produced after the final release of the
11 ## distribution.
12 deb http://fr.archive.ubuntu.com/ubuntu/ oneiric-updates main restricted
13 deb-src http://fr.archive.ubuntu.com/ubuntu/ oneiric-updates main restricted
14
15 ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
16 ## team. Also, please note that software in universe WILL NOT receive any
17 ## review or updates from the Ubuntu security team.
18 deb http://fr.archive.ubuntu.com/ubuntu/ oneiric universe
19 deb-src http://fr.archive.ubuntu.com/ubuntu/ oneiric universe
20 deb http://fr.archive.ubuntu.com/ubuntu/ oneiric-updates universe
21 deb-src http://fr.archive.ubuntu.com/ubuntu/ oneiric-updates universe
22
23 ## N.B. software from this repository is ENTIRELY UNSUPPORTED by the Ubuntu
24 ## team, and may not be under a free licence. Please satisfy yourself as to
25 ## your rights to use the software. Also, please note that software in
26 ## multiverse WILL NOT receive any review or updates from the Ubuntu
27 ## security team.
28 deb http://fr.archive.ubuntu.com/ubuntu/ oneiric multiverse
29 deb-src http://fr.archive.ubuntu.com/ubuntu/ oneiric multiverse
30 deb http://fr.archive.ubuntu.com/ubuntu/ oneiric-updates multiverse
31 deb-src http://fr.archive.ubuntu.com/ubuntu/ oneiric-updates multiverse
32
33 ## N.B. software from this repository may not have been tested as
34 ## extensively as that contained in the main release, although it includes
35 ## newer versions of some applications which may provide useful features.
36 ## Also, please note that software in backports WILL NOT receive any review
37 ## or updates from the Ubuntu security team.
38 deb http://fr.archive.ubuntu.com/ubuntu/ oneiric-backports main restricted universe multiverse
39 deb-src http://fr.archive.ubuntu.com/ubuntu/ oneiric-backports main restricted universe multiverse
40
41 deb http://security.ubuntu.com/ubuntu oneiric-security main restricted
42 deb-src http://security.ubuntu.com/ubuntu oneiric-security main restricted
43 deb http://security.ubuntu.com/ubuntu oneiric-security universe
44 deb-src http://security.ubuntu.com/ubuntu oneiric-security universe
45 deb http://security.ubuntu.com/ubuntu oneiric-security multiverse
46 deb-src http://security.ubuntu.com/ubuntu oneiric-security multiverse
47
48 ## Uncomment the following two lines to add software from Canonical's
49 ## 'partner' repository.
50 ## This software is not part of Ubuntu, but is offered by Canonical and the
51 ## respective vendors as a service to Ubuntu users.
52 # deb http://archive.canonical.com/ubuntu oneiric partner
53 # deb-src http://archive.canonical.com/ubuntu oneiric partner
54
55 ## This software is not part of Ubuntu, but is offered by third-party
56 ## developers who want to ship their latest software.
57 deb http://extras.ubuntu.com/ubuntu oneiric main
58 deb-src http://extras.ubuntu.com/ubuntu oneiric main

Tu m'en vois ravi. Bonne soirée.