Chemistry backfill should handle missing Observation during note creation #565

Context

Identified during review of #558 (558-radionuclides-backfill branch).

Problem

In chemistry_backfill.py, after the pg_insert upsert, the code looks up the just-upserted Observation using scalar_one() (line ~259). This can raise NoResultFound or MultipleResultsFound with no context about which GlobalID was being processed.

Fix

Replace scalar_one() with scalar_one_or_none() and add explicit error handling that includes the GlobalID in the error message. Append to result.errors and continue rather than crashing the entire backfill.

Files

• transfers/backfill/chemistry_backfill.py (lines 255–259)