Actually handle AttributeError and document (#896)
Actually handle AttributeError and document (#896)

Fixes #895 
PersonalGenomesOrg/open-humans,PersonalGenomesOrg/open-humans,OpenHumans/open-humans,OpenHumans/open-humans,PersonalGenomesOrg/open-humans,OpenHumans/open-humans,PersonalGenomesOrg/open-humans,OpenHumans/open-humans