I know that Diet Coke isn’t especially healthy, and that it’s almost synonymous with Trumpism. But I’m a junkie all the same — my brain associates the taste of it with feelings of normality and assurance — and right now the shortage…hell, the absence of silver Diet Coke cartons on supermarket shelves is causing a certain distress. All the other soft drinks are there in abundance — Diet Coke is the only one that’s AWOL.