Comment 31 for bug 24250

MetaRelease.py (the Python code that does the check) uses urllib2 directly, and doesn't use the apt/synaptic settings. Although urllib2 looks at the environment variables for proxy settings, sudo zaps these for security reasons. I was able to make it work by using sudo -s to get a root shell, setting the environment variables, and then running update-manager. My squid access log shows that it fetched http://changelogs.ubuntu.com/meta-release.

I believe this is a bug in MetaRelease.py, which should be changed to use the proxy settings from apt/synaptic.