Comment 12 for bug 565810

Maxence is aware of the problem. Unfortunately, it's likely that the front-end, which is what is currently down, won't be back up until Wednesday.

In the meantime, people can use one of the mirrors mentioned above (though I don't know who maintains them, nor if they are up-to-date). It's also possible to directly use one of the back-ends (which are official), like this one: 88.191.101.8 (v4), 2a01:e0b:1:101:21c:c0ff:fe65:36c4 (v6).
So you can add the following line to your /etc/hosts:
  88.191.101.8 packages.medibuntu.org
(this one also works for fr.packages.medibuntu.org)
Please, remove this line from your /etc/hosts once the front-end is back.