Proxy and Linux Mint 15 MATE

When using Linux Mint 15 MATE from behind a proxy, here is one configuration that seems to work:

• system proxy: set it using Control Center / Network Proxy.
• package manager: set it using package manager preferences. Proxy definition will be used by the update manager as well.
• language support: this is the tricky part. Neither system proxy nor package manager proxy is used. File /etc/apt/apt.conf must be created, with following contents:

Acquire::http::proxy "http://<url>:<port>/";
Acquire::ftp::proxy "ftp://<url>:<port>/";
Acquire::https::proxy "https://<url>:<port>/";