Debugging :-). Yesterday it was working. Today it said File "/app/conbench/app/benchmarks.py", line 19, in newest_of_many_results return max(results, key=lambda r: r.started_at) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ ValueError: max() arg is an empty sequence So, in the following dictionary comprehension, the function newest_of_many_results(bmrlist) was called with an empty list: newest_result_by_bname = { bname: newest_of_many_results(bmrlist) for bname, bmrlist in bmrt_cache["by_benchmark...