title: E: The repository 'http://ppa.launchpad.net/certbot/certbot/ubuntu focal Release' does not have a Release file
body: <p>Since i installed certbot on Debian 10, it always shows this error:</p>
  
  <pre><code>root@HypeTime:/home/sinusbot# apt update
  Hit:1 http://security.debian.org/debian-security buster/updates InRelease
  Hit:2 http://deb.debian.org/debian buster InRelease
  Hit:3 http://deb.debian.org/debian buster-updates InRelease
  Ign:4 http://ppa.launchpad.net/certbot/certbot/ubuntu focal InRelease
  Err:5 http://ppa.launchpad.net/certbot/certbot/ubuntu focal Release
    404  Not Found [IP: 2001:67c:1560:8008::15 80]
  Reading package lists... Done
  E: The repository 'http://ppa.launchpad.net/certbot/certbot/ubuntu focal Release' does not have a Release file.
  N: Updating from such a repository can't be done securely, and is therefore disabled by default.
  N: See apt-secure(8) manpage for repository creation and user configuration details.
  </code></pre>
  
  <p>Does someone know how to fix this error?</p>