Comment 3 for bug 175587

I did many tests with pytube and squid today and everything worked just fine for me. I was not able to get errors that you got so I will try to explain how pytube uses proxies and hopefully this will help us to decide if there is a pytube or proxy problem.

Pytube uses Python urlib which uses http_proxy variable that should be set in your environment. When you enable proxy in Preferences->network proxy you in fact add proxy settings to ~/.gconf/system/http_proxy/%gconf.xml and make it accessible for many gnome apps via gconf. That is why pytube works fine when you run it in gnome-terminal (gnome-terminal will fetch those settings) and will not run when you use pytube from menu as http_proxy is not set then.

If you want to have http_proxy set in your environment(not only for "gnome environment") you might consider adding:

export http_proxy="http://user:pass@server:port"

to file:
~/.profile

to make it available for you at every time

or to:
/etc/profile

to make setting system wide.

In order to test if your environment is ok you might use wget to try to fetch some website when http_proxy variable is set. If this works and pytube does not, then there is a bug in pytube that I cannot track at the moment so please report that and I will try to hunt it down. If wget also does not work, than your proxy settings or proxy configuration are not right.