Loader silently fails during unique key lookup

[znatty22]

The loader is silently failing in this step:

kf-lib-data-ingest/kf_lib_data_ingest/etl/load/load_base.py

Line 254 in 5f8cf2a

try:

because the key lookup is enclosed in a generic try/except causing it to miss real exceptions.

This recently happened when it tried to create the key for a phenotype using the event age but a ValueError was thrown due to an invalid int conversion. The ValueError was hidden due to the line above and the ingest library user did not know why the phenotype was not loaded.

We should make a custom exception that gets thrown for known error conditions during unique key lookup