AFAIK only the primary archive has the atomic dists update functionality, so partner doesn't have dists.new. This upsets 10-sign-releases and 20-remove-uncompressed-listings, both of whom expect to work in dists.new.
2011-04-06 06:55:13 DEBUG Executing: env PATH="$PATH:/srv/launchpad.net/codelines/trunk/cronscripts/publishing" DISTSROOT=/srv/launchpad.net/ubuntu-archive/ubuntu-partner/dists ARCHIVEROOT=/srv/launchpad.net/ubuntu-archive/ubuntu-partner run-parts -- '/srv/launchpad.net/codelines/current/cronscripts/publishing/distro-parts/ubuntu/publish-distro.d'
find: `/srv/launchpad.net/ubuntu-archive/ubuntu-partner/dists.new': No such file or directory
run-parts: /srv/launchpad.net/codelines/current/cronscripts/publishing/distro-parts/ubuntu/publish-distro.d/10-sign-releases exited with return code 1
find: `/srv/launchpad.net/ubuntu-archive/ubuntu-partner/dists.new': No such file or directory
run-parts: /srv/launchpad.net/codelines/current/cronscripts/publishing/distro-parts/ubuntu/publish-distro.d/20-remove-uncompressed-listings exited with return code 1
Wed, 06 Apr 2011 06:55:14 +0000: Copying the indices into place.
2011-04-06 06:55:14 DEBUG Command returned 256.
2011-04-06 06:55:14 DEBUG Command failed: Failure while executing run-parts /srv/launchpad.net/codelines/current/cronscripts/publishing/distro-parts/ubuntu/publish-distro.d.
Although it did say this first:
2011-04-06 06:55:09 DEBUG Overriding dists root with /srv/launchpad.
There was nothing to publish, so it wasn't created, I guess. Which suggests that the rsync isn't working either.