Comment 8 for bug 479391

I also confirm that the problem is (meanwhile?) independent of a proxy having authentication or not. I tested both cases.

do-release-upgrade works (!), but it needs ages directly after the start. In my opinion it is waiting for a timeout.

The problem lies still in url_downloadable. If this function returns false, do-release-upgrade falls back to the main server. The remaining part of the application runs happily (and fast) with that fallback.

url_downloadable seems to block on some systems, waiting for a timeout. Thus it may last a very long time before the programm continoues. Maybe this depends on the network or the proxy or its configuration.

The fallback code exists in _expandUri. Modifiying the code that it always just returns the fallback server (= it doesn't use url_downloadable directly or indirectly anymore) resolves the problem immediately.

The patch from Thomas (#5) also works, but in my opinion it removes the support of ftp uris?