remote: HEAD is now at 44538cb... nginx dokku
nginx app detected
Ign http://archive.ubuntu.com quantal InRelease
Ign http://archive.ubuntu.com quantal-updates InRelease
Ign http://archive.ubuntu.com quantal-security InRelease
Ign http://archive.ubuntu.com quantal Release.gpg
Ign http://archive.ubuntu.com quantal-updates Release.gpg
Ign http://archive.ubuntu.com quantal-security Release.gpg
Ign http://archive.ubuntu.com quantal Release
Ign http://archive.ubuntu.com quantal-updates Release
Ign http://archive.ubuntu.com quantal-security Release
Err http://archive.ubuntu.com quantal/main amd64 Packages
404 Not Found [IP: 91.189.91.23 80]
Err http://archive.ubuntu.com quantal/universe amd64 Packages
404 Not Found [IP: 91.189.91.23 80]
Err http://archive.ubuntu.com quantal-updates/main amd64 Packages
404 Not Found [IP: 91.189.91.23 80]
Err http://archive.ubuntu.com quantal-updates/universe amd64 Packages
404 Not Found [IP: 91.189.91.23 80]
Err http://archive.ubuntu.com quantal-security/main amd64 Packages
404 Not Found [IP: 91.189.91.23 80]
Err http://archive.ubuntu.com quantal-security/universe amd64 Packages
404 Not Found [IP: 91.189.91.23 80]
remote: W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/quantal/main/binary-amd64/Packages 404 Not Found [IP: 91.189.91.23 80]
remote:
remote: W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/quantal/universe/binary-amd64/Packages 404 Not Found [IP: 91.189.91.23 80]
remote:
remote: W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/quantal-updates/main/binary-amd64/Packages 404 Not Found [IP: 91.189.91.23 80]
remote:
remote: W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/quantal-updates/universe/binary-amd64/Packages 404 Not Found [IP: 91.189.91.23 80]
remote:
remote: W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/quantal-security/main/binary-amd64/Packages 404 Not Found [IP: 91.189.91.23 80]
remote:
remote: W: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/quantal-security/universe/binary-amd64/Packages 404 Not Found [IP: 91.189.91.23 80]
remote:
remote: E: Some index files failed to download. They have been ignored, or old ones used instead.
The reason is, very likely you have old buildstep based on Ubuntu 12.04 and it's no longer supported. You need to update buildstep, check details here.
I get this error, on an otherwise vanilla setup.