pre_devergence: update usage() description
pre_devergence: update usage() description


Former-commit-id: db7e33cab868a2553d4446f603ab088bd11e9cd1 [formerly 6994a4cb18a3ee55fc5bd982f37358dd6a5f401c]
Former-commit-id: a07650e3a85daf487b427c1da5138908d72ff118
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine