I found out why you're getting this error as I'm also receiving this error.
This is the message from the libGDX site:
The old setup UI has been deprecated, the audio and image extensions have been removed, and the demos have been gradelized and put into their own repositories. You can now also directly test the demos in your browser (or desktop, or Android device)!
It seems that libgdx is officially in version 1.0 and no longer storing previous updates or config files in their repository. Now you need to update to version 1.0 and follow the instructions on how to setup here: