Linux error messages are usually pretty easy to understand, actually. The message is correctly and accurately telling you that "wordnet" is not available in the Ubuntu 13.04 software libraries.
Let's use Google to see why this might be the case? A quick search located this article:
http://fridge.ubuntu.com/2014/01/28/...nuary-27-2014/
Quote:
|
This is a follow-up to the End of Life warning sent last month to confirm that as of today (Jan 27, 2014), Ubuntu 13.04 is no longer supported. No more package updates will be accepted to 13.04, and it will be archived to old-releases.ubuntu.com in the coming weeks.
|
So the answer is simple: Ubuntu 13.04 is dead and you need to upgrade.
http://www.ubuntu.com/download/desktop/upgrade
