show a friendly message when the submission request fails

[Sheila Miguez]

The submission service returns responses with a message.

Example:
{
"result":false,
"code":"missing_json",
"message":"Submission json file is missing"
}

If a failure comes from the submission-service part of the stack, it will include the message. If the failure comes from earlier in the stack, it likely won't; so be cautious when assuming that there will be a message.