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I am using Ubuntu MATE. I am trying to open Ubuntu Software & Updates and Software Updater. So, I clicked on Control Center and I am clicking on Software & Updates and Software Updater. But they are not opening.

What's the problem and how can I fix it?

sudo apt update
[sudo] password for souvik: 

...               
Err:7 http://ppa.launchpad.net/cassou/emacs/ubuntu xenial Release              
  404  Not Found
...                                                  
E: The repository 'http://ppa.launchpad.net/cassou/emacs/ubuntu xenial Release' does not have a Release file.

Thanks and Regards

Zanna
  • 70,465
Souvik Maity
  • 31
  • Please open terminal and execute sudo apt update. And add error output to the question (if any). What is your Ubuntu version? – N0rbert Oct 27 '18 at 21:04
  • I am using "MATE Desktop Environment 1.12.1". I am getting the following error after that command "sudo apt update".Err:7 http://ppa.launchpad.net/cassou/emacs/ubuntu xenial Release
    404 Not Found     – Souvik Maity Oct 27 '18 at 21:10

1 Answers1

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The PPA from your error message is outdated and no longer maintained, so we need to remove it with commands below:

sudo apt install ppa-purge
sudo ppa-purge ppa:cassou/emacs

if this command fails - remove this PPA from the system with another command: 

sudo add-apt-repository -r ppa:cassou/emacs

And then you can use your system as before. As starting point you may want to install all updates:

sudo apt update
sudo apt upgrade
N0rbert
  • 99,918
  • Thanks for the response. But the first two commands are not working. E: Failed to fetch http://ppa.launchpad.net/cassou/emacs/ubuntu/dists/xenial/main/binary-amd64/Packages 404 Not Found – Souvik Maity Oct 28 '18 at 07:34
  • Then try to remove this PPA from the system with other command: sudo add-apt-repository -r ppa:cassou/emacs. – N0rbert Oct 28 '18 at 07:43
  • Now it is showing this..... File "/usr/lib/python3/dist-packages/softwareproperties/SoftwareProperties.py", line 27, in ModuleNotFoundError: No module named 'apt_pkg' – Souvik Maity Oct 30 '18 at 06:40
  • Then you should reinstall one package with sudo apt-get install --reinstall python3-apt. – N0rbert Oct 30 '18 at 08:47
  • I tried with that command and then I did sudo apt update and it showing me "Updating from such a repository can't be done securely, and is therefore disabled by default". Then I use the command sudo add-apt-repository -r ppa:cassou/emacs but as usual it is showing "ModuleNotFoundError: No module named 'apt_pkg' ". – Souvik Maity Oct 31 '18 at 08:23