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I am unable to add a repository via the command line on Ubuntu 14.04. Apt-get works perfectly fine, and I am able to update the system. I have configured my /etc/apt/apt.config file as follows:
Acquire::http::proxy "http://<username>:<password>@<proxy address>:<port>/";
For example, when trying to add the repository for y-ppa-manager, I receive:
add-apt-repository ppa:webupd8team/y-ppa-manager Cannot add PPA: 'ppa:webupd8team/y-ppa-manager'. Please check that the PPA name or format is correct.
If you need any more info., feel free to ask.