strange "alert" in game

[Lexi357]

Hi!
I was just wondering if anyone else has had any strange slerts in game since LU38.
I noticed the other night, once while buffing and then once just after I zoned into Kaladim. The text says something about needing a designer to create a custom string... sorry I can't remember the exact phrasing.

Im wondering if it is something that changed with the lu and is conflicting with my UI or if it might be a custom macro im using that is now..."wrong"
I didn't notice any kind of problems with the exception of the message in my chat box, it is still quite unerving not to mention irritating.
If anyone has a clue as to what it might be refering to or how I might (fix) the problem, could you give me some advice please?
Thank you!
Lexi