REST API calls are not returning any response text

When an API call results in an error, the HTTP response that is returned to the client typically will not contain text in the response body.

When developing API clients, developers should refer to the response code to determine success / failure of the API call, and refer to the response headers for specific information on failures. 

For details, please refer to:
https://truecontext.zendesk.com/entries/21017302-04-error-handling