Adjust handling of categories in import_datasets to not depend on removed path field.
Adjust handling of categories in import_datasets to not depend on removed path field.

sunlightlabs/hall-of-justice,dmc2015/hall-of-justice,sunlightlabs/hall-of-justice,dmc2015/hall-of-justice,sunlightlabs/hall-of-justice,dmc2015/hall-of-justice