utils/serializer: Fix exception handling in Python3
utils/serializer: Fix exception handling in Python3

Allow for the fact that exceptions do not have a 'message' attribute in
Python3.

setrofim/workload-automation,ARM-software/workload-automation,lisatn/workload-automation,ARM-software/workload-automation,ARM-software/workload-automation,lisatn/workload-automation,lisatn/workload-automation,setrofim/workload-automation,ARM-software/workload-automation,setrofim/workload-automation,setrofim/workload-automation,lisatn/workload-automation