Definitely not an upgrade-system bug. Leaving package name blank and subscribing ubuntu-installer as suggested by mdz.
** Changed in: upgrade-system (Ubuntu) Sourcepackagename: upgrade-system => None -- Usage problems in install partitioner https://launchpad.net/bugs/66175 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
