According to https://lists.ubuntu.com/archives/ubuntu-translators/2006-October/000872.html, this string is in libapt-pkg3.51. I found it in Rosetta : https://launchpad.net/ubuntu/edgy/+source/apt/+pots/libapt-pkg3.51/fr/148/+translate but it seems already translated.
-- Untranslated string in french https://launchpad.net/bugs/78012 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs