Over the past couple of hours APT whitelisting on our container-based infrastructure failed. The incident is related to the GitHub.com outage earlier tonight. Some components weren't able to reach data that's currently being pulled from GitHub to manage APT whitelisting. This affected a good 50% of builds running on travis-ci.org and all builds running on travis-ci.com.
We'll investigate how to reduce this dependency and the likelihood of a GitHub.com failure to impact package installations like this.