do-release-upgrade for 12.04 to 14.04 fails

[Mark]

I recently successfully upgraded an Lubuntu 11.10 x86-64 installation to 12.04.

$ lsb_release -rd
Description: Ubuntu 12.04.5 LTS
Release: 12.04

Now I want to update from 12.04 to 14.04. However on running do-release-upgrade I consistently see the same error. It seems to be a network-related problem, but I have tried several times over the last few weeks with the same result each time. There are also some messages about being unable to rename files.

I have attached the full console output on running do-release-upgrade.

Some lines from that which may be relevant:

Error during update

A problem occurred during the update. This is usually some sort of
network problem, please check your network connection and retry.

W:Failed to fetch
copy:/var/lib/apt/lists/partial/archive.canonical.com_ubuntu_dists_trusty_partner_i18n_Translation-en
rename failed, No such file or directory
(/var/lib/apt/lists/archive.canonical.com_ubuntu_dists_trusty_partner_i18n_Translation-en.gz.gz
->
/var/lib/apt/lists/archive.canonical.com_ubuntu_dists_trusty_partner_i18n_Translation-en.gz).
[... many similar lines...]
, E:Some index files failed to download. They have been ignored, or
old ones used instead.

[Ubuntu Foundations Team Bug Bot (crichton)]

Thank you for taking the time to report this bug and helping to make Ubuntu better. It seems that your bug report is not filed about a specific source package though, rather it is just filed against Ubuntu in general. It is important that bug reports be filed about source packages so that people interested in the package can find the bugs about it. You can find some hints about determining what package your bug might be about at https://wiki.ubuntu.com/Bugs/FindRightPackage. You might also ask for help in the #ubuntu-bugs irc channel on Freenode.

To change the source package that this bug is filed about visit https://bugs.launchpad.net/ubuntu/+bug/1392869/+editstatus and add the package name in the text box next to the word Package.

[This is an automated message. I apologize if it reached you inappropriately; please just reply to this message indicating so.]