Idiom for making fun of an unpleasant situation?

Solution 1:

One modern proverb that may be suitable for this situation is "If life hands you lemons, make lemonade." The idea is that with the right attitude (and the right ingredients) you can turn something sour into something sweet.

Charles Doyle, Wolfgang Mieder & Fred Shapiro, The [Yale] Dictionary of Modern Proverbs dates the expression to 1910:

If life hands you lemons, make lemonade. [First cited occurrence:] 1910 William G. Haupt, The Art of Business College Soliciting (Chicago: for the author) 89: "Don't be a pessimist, but be optimistic. If anyone 'hands you a lemon' take it home and make lemonade of it." ...

Solution 2:

Making light of the situation

This is one of the more common expressions where someone is trying to downplay the seriousness or the negativity of a situation.

Solution 3:

I'd say whistling past the graveyard, and Wiktionary agrees, but I think that has connotations of being unaware of the full gravity of the situation.