I was having a look at the original paper on supergravity by Ferrara, Freedman and van Nieuwenhuizen available here. The abstract has an interesting line saying that
Added note: This term has now been shown to vanish by a computer calculation, so that the action presented here does possess full local supersymmetry.
But the paper was written in 1976! Do you have any info what kind of computer and computer algebra system did they use? Is it documented anywhere?