State handler errors are not logged well

[cicdw]

Example:

from prefect import task, Flow

def handler(*args, **kwargs):
    raise SyntaxError("unique informative message")

@task(state_handlers=[handler])
def my_task():
    pass

f = Flow("reproducible-example", tasks=[my_task])

f.run()

# INFO - prefect.FlowRunner | Beginning Flow run for 'reproducible-example'
# INFO - prefect.FlowRunner | Starting flow run.
# DEBUG - prefect.FlowRunner | Flow 'reproducible-example': Handling state change from Scheduled to Running
# INFO - prefect.TaskRunner | Task 'my_task': Starting task run...
# DEBUG - prefect.TaskRunner | Task 'my_task': Handling state change from Pending to Running
# INFO - prefect.TaskRunner | Task 'my_task': finished task run for task with final state: 'Failed'
# INFO - prefect.FlowRunner | Flow run FAILED: some reference tasks failed.
# DEBUG - prefect.FlowRunner | Flow 'reproducible-example': Handling state change from Running to Failed

We should see an ERROR log displaying a repr of the exception that was thrown inside the state handler.