I don't know if you know this fable of Aesop but from this we have a very famous expression in Greek: "ότι δεν πιάνει η αλεπού τα κάνει κρεμαστάρια" which means: "Pretending that one doesn't want something, because one does not or cannot have it.".
In English the expression is "sour grapes".
Do you have any similar expression in Russian?