fix single-element tuples
fix single-element tuples


Former-commit-id: 1122885f07a41bdcf57a6aaacafc8927e3b67006 [formerly 5c6ca2734c8e612705267fccdb8bd442958c062a]
Former-commit-id: cd562d29971ef3b66b85eae7157a5b597266316a
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine