use http.HTTPStatus for readability

stand/api.py

@@ -1,4 +1,5 @@
 from datetime import datetime
+from http import HTTPStatus
 from typing import Any
 
 import pandas as pd
@@ -20,7 +21,7 @@ def append(beamline: Beamline, pgroup: PGroup, run: int, row: dict[str, Any]):
 
     run_exists = not lib.read(pgroup, date_range=index, columns=[]).data.index.empty
     if run_exists:
-        raise HTTPException(409, f"run {run} exists already in {beamline}/{pgroup}")
+        raise HTTPException(HTTPStatus.CONFLICT, f"run {run} exists already in {beamline}/{pgroup}")
 
     timestamp = row.pop("timestamp", None)
     timestamp = datetime.fromisoformat(timestamp) if timestamp else datetime.now()