The job on Ubuntu 14.04 was running fine and suddenly stopped working with the following error:
Reading package lists... 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 https://packages.microsoft.com/ubuntu/14.04/prod/dists/trusty/main/binary-amd64/Packages.gz Hash Sum mismatch E: Some index files failed to download. They have been ignored, or old ones used instead. The command "sudo -E apt-get -yq --no-install-suggests --no-install-recommends $(travis_apt_get_options) install powershell" failed and exited with 100 during .
The .travis.yml is here.