Sentiment Analysis: Error Message

How can I address the following error message in a sentiment model (WARNING: Kernel Model: The given example set does not contain a regular attribute with name 'messag'. This might cause problems for some models depending on this particular attribute.). I replicated a sentiment model from a YouTube video (http://www.youtube.com/watch?v=4EWXf3_0ta4) where the same error message occurs. So I was wondering whether I can disregard the error message, given that others, maybe more experienced users, get the same result or if there is a fix.

Thanks for any suggestions.

Peter