Issue
On 1/1/2017 two popular buildpacks authored by David Dollar (ddollar) -- heroku-buildpack-apt and heroku-buildpack-multi -- are set to expire, which means new builds using these buildpacks will fail.
Resolution
Apt buildpack - github
This buildpack is used for installing packages from apt. As a replacement we suggest you use Herokus apt buildpack.
Multi buildpack - github
This buildpack is used for setting multiple buildpacks on an app. It is no longer necessary, as Heroku has native support for multiple buildpacks.
If for some reason you need to continue using a .buildpacks file (not recommended) you can use the Heroku fork here: https://github.com/heroku/heroku-buildpack-multi
How do I add or remove a buildpack?
Learn more about adding and removing a buildpack.