I got the same error message with Tableau 10.1 and Tableau 10.3 Beta.
Although the issue is not fixed, clear out the cache of web browser and refresh the page, and you will no more see the error.
Hope it works for you.
Not working for me, but thanks for the post.
I am still getting this error with tableau server version 10.3.1
Switching User (i.e. logging out and logging back in again) resolves the error as a workaround.
Mine just started working again...