Investigate netmhccons `len(peptide_list) != len(scores)` error

@malachig ran 604 pvacseq jobs with NetMHCcons. Out of those, 13 failed with the error above. When retrying the jobs with the existing output directory, picking up at the failure point, all jobs succeeded. This leads us to believe that error is sporadic and could be caught and retried.

I previously added https://github.com/griffithlab/pVACtools/blob/da18907e82f19825fe5479a2e94f037c12fd53d2/lib/call_iedb.py#L52 to catch and retry this error but it seems to not working as intended. We should do the following:

• Confirm whether or not the above code catches this error (as opposed to the retry also failing and erroring out).
  • If it does:
    • Investigate whether we should retry a couple of times instead of just once.
  • If it does not:
    • Check the latest version of IEDB to see if they implement any sort of retrying on their end. If not, suggest this as a feature addition.
    • Update the above code to catch the error correctly

Start in lib/call_iedb.py at the retry logic around line 52 and determine whether it catches the NetMHCcons len(peptide_list) != len(scores) error or only retries unsuccessfully. Check the latest IEDB behavior, then verify the retry count and error handling against the reported sporadic failures; done means the error is correctly caught and retried or the external limitation is documented.