🐛 fix bug in migration script with simple sources
🐛 fix bug in migration script with simple sources

also adds some additional checking and logs some output along the way.

PersonalGenomesOrg/open-humans,OpenHumans/open-humans,OpenHumans/open-humans,PersonalGenomesOrg/open-humans,OpenHumans/open-humans,OpenHumans/open-humans,PersonalGenomesOrg/open-humans,PersonalGenomesOrg/open-humans