It’s a mediocre film, but in a larger sense, it’s good that Clint Eastwood made “The 15:17 to Paris” (2018). It’s good to tell this story to a wide audience. Most young people don’t sit around on porches or at barbershops or the local diner and listen to older, wiser folk pass along wisdom, so if it takes a movie about three young adult American tourists who stepped into the breach and helped thwart a terrorist attack on a train to teach kids it takes more than snarky Twitter comments to make the world a better place, so be it.