After “a very bad year,” Paris tour operator Marc Vernhet sees a ray of light with the promised return of tourists from the United States and elsewhere who are welcome in France as of Wednesday if they have been vaccinated against the coronavirus. His agency, 2CVParisTour.com, is starting to get bookings again from Americans for its sightseeing tours conducted in quirky, bug-eyed Citroen cars. June is still very lean, but July is looking better,...