We already know this rule: You aren’t permitted to leave a museum without running into a gift shop. I also discovered late last week in Paris that you can’t walk out of the newly restored Notre-Dame cathedral without passing a large gift zone near the arrow that points to Sortie de secours. And you can’t even leave a country, really, without exiting passport control on the way to the gate and passing — not by, but through — a duty-free shopping zone through which snakes a zig-zaggy path to your gate. Before you leave anywhere, in other words, there’s a gentle shakedown, with shiny objects (museum jewelry, clickety-clacky rosaries, bottles of perfume, you get the idea) distracting you on the way to the exit.