"apt-get update" fails due to Ubuntu 18.10 being no longer supported

[mcejp]

Started errorring out today:

$ apt-get update
Ign:1 http://archive.ubuntu.com/ubuntu cosmic InRelease
Ign:2 http://archive.ubuntu.com/ubuntu cosmic-updates InRelease
Ign:3 http://security.ubuntu.com/ubuntu cosmic-security InRelease
Ign:4 http://archive.ubuntu.com/ubuntu cosmic-backports InRelease
Err:5 http://security.ubuntu.com/ubuntu cosmic-security Release
  404  Not Found [IP: 91.189.88.174 80]
Err:6 http://archive.ubuntu.com/ubuntu cosmic Release
  404  Not Found [IP: 91.189.88.173 80]
Err:7 http://archive.ubuntu.com/ubuntu cosmic-updates Release
  404  Not Found [IP: 91.189.88.173 80]
Err:8 http://archive.ubuntu.com/ubuntu cosmic-backports Release
  404  Not Found [IP: 91.189.88.173 80]
Reading package lists...
E: The repository 'http://security.ubuntu.com/ubuntu cosmic-security Release' no longer has a Release file.
E: The repository 'http://archive.ubuntu.com/ubuntu cosmic Release' no longer has a Release file.
E: The repository 'http://archive.ubuntu.com/ubuntu cosmic-updates Release' no longer has a Release file.
E: The repository 'http://archive.ubuntu.com/ubuntu cosmic-backports Release' no longer has a Release file.