The fictional town of Wiley, Oregon, is 513 miles from the Pacific coast. Measured as the crow flies, that would put it in Idaho, but the freewheeling road-trip movie Gasoline Rainbow is not about taking the direct route, and Wiley is as much an idea as it is a location, anyway. It’s where teenagers Tony Aburto, Micah Bunch, Nichole Dukes, Nathaly Garcia, and Makai Garza (the characters share names with the first-time actors playing them) grew up and feel constrained by, for...