The strong showing achieved by leftist groups in France’s elections was a shock to some, but less so to those who’ve read “Submission,” the 2015 novel by Michael Houellebecq. It envisioned France in the aftermath of a bloodless revolution that brought Islamists to power. Now it is a former Trotskyite, Jean-Luc Mélenchon, who has the wind at his back and promises to recognize “Palestine” tumbling from his lips. Life is catching up to art.