Cost WDL should throw on FISS API errors [VS-518]

[mcovarr]

% python3 workflow_compute_costs.py \
    --workspace_namespace 'not' \                            
    --workspace_name 'there'                
Traceback (most recent call last):
  File "workflow_compute_costs.py", line 135, in <module>
    costs = compute_costs(args.workspace_namespace, args.workspace_name, args.exclude)
  File "workflow_compute_costs.py", line 32, in compute_costs
    submissions = list_submissions(workspace_namespace, workspace_name)
  File "workflow_compute_costs.py", line 14, in fapi_list_submissions
    return fapi_error_check(fapi.list_submissions(workspace_namespace, workspace_name))
  File "workflow_compute_costs.py", line 8, in fapi_error_check
    raise Exception(j['message'])
Exception: workspace not/there does not exist or you do not have permission to use it

[codecov]

Codecov Report

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[mcovarr]

let errors go to stderr where users can more easily see them in the job logs