Bring tissues. For if you need a good ugly-cry in a still-young year that has already been filled with so much grief, “Supernova” is your movie. Which isn’t to say that this incredibly heartfelt and sad film isn’t good—far from it.

This new film from writer-director Harry Macqueen stars Colin Firth and Stanley Tucci as Sam and Tusker, longtime romantic partners in late middle age on a road trip through