sudo add-apt-repository throws an exception

Solution 1:

You have to define proxy environment variable and tell sudo to use it (with -E flag):

export http_proxy=http://<proxy>:<port>
export https_proxy=http://<proxy>:<port>
sudo -E add-apt-repository ppa:team-xbmc/ppa

If you have to use username and password for proxy, use this syntax:

export https_proxy=<username>:<password>@<proxy>:<port>