Joined Cases C-593/15 P and C-594/15 P: Judgment of the Court (Fourth Chamber) of 25 October 2017 — Slovak Republic v European Commission (Appeal — Own resources of the European Union — Decision 2007/436/EC — Financial liability of the Member States — Loss of certain import duties — Obligation to pay the European Commission the amount corresponding to the loss — Actions for annulment — Admissibility — Letter from the European Commission — Concept of ‘actionable measure’)