Who have you rented your game server from? Most game server hosts do not allow B3 on their system for security reasons. It is best to do a b3 install on another server that allows you to install python scripts.
If you want a place that has everything, try LPGS as mentioned here: http://www.bigbrotherbot.net/hosting
But from my experience, my setup suites my needs best. I had to cancel with LPGS because they didn't meet my needs.
- Renting game server (running Urban Terror)
- Renting VPS (installed B3 here)
If you rented from gameservers.com, then I can tell you that they do not support B3 on their servers. If your game server host is not gameserver.com then you should ask them if they allow b3 to be installed. Try the forums associated with your game server and don't hesitate to open a support ticket there, it's your server and you need to know things.