Network Manager is unable to setup proxy credentials for apt-get

[Michael Kunzmann]

Ubuntu Release: 12.10
Network-Manager Version: 0.9.6.0-0ubuntu7

When I setup my proxy settings like this one:

Host: user:<email address hidden>
Port: 8080

Then, $http_proxy will be exported correctly to http://user:<email address hidden>:8080/
But /etc/apt/apt.conf gets NO entry.

But when I leave username and password away, apt.conf gets an entry as expected: Acquire::http::proxy "http://sub.domain.tld:8888/";

My current workaround is to edit apt.conf manually after setting up my proxy settings in the network manager.