Better usage messages from make_source.
Better usage messages from make_source.



Former-commit-id: 0fdb64f715fc7c7273e7733d051438caf92ab761
julie-sullivan/phytomine,julie-sullivan/phytomine,julie-sullivan/phytomine,julie-sullivan/phytomine,julie-sullivan/phytomine,julie-sullivan/phytomine,julie-sullivan/phytomine