I build, test and deploy at CircleCI.
Our code needs outside packages so I install it at CircleCI.
I use package manager to install those packages, apt, npm, gem, npm and so on.
But one of them are failed at the external server error. ( package not found with 404)
So a building is failed at a time. (success at other time)
Could you give me some ideas or your practice to avoid it?
e.g. Include all packages into a container image