An Argentinian reader has kindly corrected my reference to the "make a mess" quotation. I put "Vaya lío!" Apparently that means "What a mess!", is an expression that belongs to Spanish Spanish, and is not an expression that Argentinians would use. What the Holy Father said was "Hagan lío!" which could be translated as "Go, make a mess", though my correspondent thinks that "lío" would have a slightly more positive connotation than "mess." So "Go, stir things up" might be better.
Here is a link to a Youtube video of the speech of Pope Francis to young people on 25 July 2013 (embedding is disabled.)
I have corrected the post now.