After reading the bug report I am surprised so many people are using a remote package repositories for their build machines builds... then again I'm not too surprised I guess.

I'm not that familiar with Docker but I am of package/dep management (from deb, jars, npm, eggs etc) and you most certainly want to use a mirrored package repository (jfrog, sonatype, or whatever) for this reason and many more other reasons (bandwidth, security, control, etc).

So if you did have issues with the outage I would look into one of those mirroring tools. At the minimum it will speed up your builds.