We have restored apt.dockerproject.org source. You are now able to install APT packages from this source.
Posted Nov 16, 2016 - 18:08 UTC
Update
We've deployed a temporary workaround to disable the Docker apt repository. Docker is also keeping us updated as they work with AWS to resolve the infrastructure issues. You can follow https://github.com/travis-ci/travis-ci/issues/6881 for more frequent updates.
Posted Nov 16, 2016 - 15:39 UTC
Identified
Currently there are issues apt.dockerproject.org's CDN, which cause apt-get update to fail with `gnutls_handshake() failed: Handshake failed`. We're deploying a workaround, https://github.com/travis-ci/travis-ci/issues/6881, while Docker and AWS work to resolve the infrastructure issue.