Added note about why we check the client version way before using it

mydata_benchmarks/views/benchmark_api.py

@@ -34,6 +34,8 @@ def benchmark_submit_view(request):
         # TODO(Sybren): give feedback with validation errors to the caller.
         return JsonResponse({'message': 'The submitted data is not valid.'}, status=422)
 
+    # Check this before forwarding the request to Open Data, so that an
+    # out-of-date warning in the log is logged before other potential errors.
     client_version, client_outdated = _is_client_version_outdated(request, benchmark_data)
 
     url = opendata.url('api/benchmarks/')