In the general hook for ubuntu there is the following code:
log = '/var/log/dist-upgrade/main.log'
if os.path.exists(log):
mtime = os.stat(log).st_mtime
human_mtime = time.strftime('%Y-%m-%d', time.gmtime(mtime))
delta = time.time() - mtime
# Would be nice if this also showed which release was originally installed
report['UpgradeStatus'] = 'Upgraded to %s on %s (%d days ago)' % (release_codename, human_mtime, delta / 86400)
else:
report['UpgradeStatus'] = 'No upgrade log present (probably fresh install)'
This does no checking of main.log to see if the upgrade was actually successful, so if someone is reporting a bug about a failed upgrade of ubuntu-release-upgrader they'll have a confusing 'UpgradeStatus' of today for the previous release.
One thing to do might be to check main.log for "ERROR" and if that exists set 'UpgradeStatus' to unknown.