Unreachable Error handling

[hkmatsumoto]

The observed behavior

We have some lines that handles requests.exceptions.MissingSchema, but unfortunately, these lines will be never called because submission_details_request has a except clause for requests.exceptions.RequestException which is a superset of requests.exceptions.MissingSchema.
This means, if a submission has no result, the program shows the unintended error message "Could not establish a connection to EvalAI." instead of the intended error message "The Submission is yet to be evaluated."

The expected behavior

If a submission has no result, the program must show the intended error message "The Submission is yet to be evaluated.".