Improved error message [skip CI]
Improved error message [skip CI]


Former-commit-id: 60b5870a372d936aa5daa2cdd1d9f9fe62967d61 [formerly 8f5c841b92338653acb55c809503e3e6c77a9c88]
Former-commit-id: c2dd909a65950f1c0860a994e0a840e7b12e9ffa
gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine,gem/oq-engine