meta-release can be corrupted on network error

[fuscata]

I had trouble upgrading my laptop from 11.04 to 11.10:

# do-release-upgrade
Checking for a new ubuntu release
No new release found

I checked /var/lib/update-manager/meta-release only to find the HTML source of a wi-fi paywall splash page.

The process that fetches this file should check that it's valid before downloading.

Related: https://bugs.launchpad.net/ubuntu/+source/update-manager/+bug/521765

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Alessander Botti Benevides (alessanderbotti)]

In my case, both /var/lib/update-manager/meta-release and /var/lib/update-manager/meta-release-lts were corrupted. I renamed these files to backup them and then ran muon (the package manager of Kubuntu 11.10), what created new files and fixed the problem.

[Alessander Botti Benevides (alessanderbotti)]

I had the same issue for upgrading Kubuntu 12.10 to 13.04. However, my previous solution did not work. Following a hint given on [1], I did
$ export DEBUG_UPDATE_MANAGER=true
$ do-release-upgrade -c
and noticed the line:
reading file '/home/username/.cache/update-manager-core/meta-release'

So, I removed '/home/username/.cache/update-manager-core/meta-release' and did do-release-upgrade -c again and it fixed both
"/home/username/.cache/update-manager-core/meta-release" and "/var/lib/update-manager/meta-release".

[1] https://bugs.launchpad.net/ubuntu/+source/update-manager/+bug/653412