def _read_response(self,response, field="<STR_LIT>"):
try:<EOL><INDENT>message = json.loads(response._content.decode('<STR_LIT:utf-8>'))[field]<EOL><DEDENT>except:<EOL><INDENT>message = response.reason<EOL><DEDENT>return message<EOL>
attempt to read the detail provided by the response. If none, 
        default to using the reason