Tesla 2019.20.1—Honk if your door is open
Right on the heels of one solution to knowing if your doors didn't close, Tesla has baked-in their own fix.
The latest release includes an option of a lock confirmation sound. Admittedly, in the past I've always found the short-honk-on-lock annoying, but after several recent incidents of doors not closing, I quickly enabled the new option.
The car now does a quick honk when it successfully (closes) and locks the doors; if the doors don't close, it'll sound a double-honk indicating a problem (e.g. an obstruction)—or it will make no sound, since it didn't realize you walked away and it's supposed to close the doors. It's probably a good idea still to not rely on the self-closing door feature.