Errors from ServiceX that aren't JSON do not tell us much

[gordonwatts]

As a user I want to be able to understand what errors are comming back from servicex when the service totally fails:

• The request ID
• If the response isn't in JSON, it would be good to have the HTML dumped instead.

[AndrewEckart]

I like the example of the Twilio API here, i.e. we should use correct HTTP status codes and send back a JSON body containing additional information (I think we already do this in many cases). We shouldn't send back HTML if there is an error requesting an API resource.

The frontend client can then use conditional logic to raise an appropriate ServiceXException, passing on the message from the server.

[gordonwatts]

That would be fine - one would need to add a story to the servicex app that scans for all "exceptions" and make sure they come back properly.