Travis is broken for stable branches (2.4 and 2.5)

[Algunenano]

11.51s$ sudo apt-get update -qq
W: The repository 'http://archive.ubuntu.com/ubuntu artful Release' does not have a Release file.
W: GPG error: https://packagecloud.io/github/git-lfs/ubuntu trusty InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY 6B05F25D762E3157
W: The repository 'https://packagecloud.io/github/git-lfs/ubuntu trusty InRelease' is not signed.
W: There is no public key available for the following key IDs:
6B05F25D762E3157  
W: http://ppa.launchpad.net/couchdb/stable/ubuntu/dists/trusty/Release.gpg: Signature by key 15866BAFD9BCC4F3C1E0DFC7D69548E1C17EAB57 uses weak digest algorithm (SHA1)
E: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/artful/main/binary-amd64/Packages  404  Not Found [IP: 91.189.88.161 80]
E: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/artful/main/binary-i386/Packages  404  Not Found [IP: 91.189.88.161 80]
E: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/artful/restricted/binary-amd64/Packages  404  Not Found [IP: 91.189.88.161 80]
E: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/artful/restricted/binary-i386/Packages  404  Not Found [IP: 91.189.88.161 80]
E: Failed to fetch http://archive.ubuntu.com/ubuntu/dists/artful/universe/binary-amd64/Packages  404  Not Found [IP: 91.189.88.161 80]
E: Some index files failed to download. They have been ignored, or old ones used instead.
The command "sudo apt-get update -qq" failed and exited with 100 during .

We have to either look for different packages or migrate those branches to use Docker too.

[Raul Marin]

In 17515:

Travis: Use xenial as distribution and bionic repos

References #4426

[Raul Marin]

In 17516:

Fix travis build

Closes #4426

[robe]

Milestone renamed