SparkPost not returning error code or error on email generation failure - sparkpost

Question

I am trying to implement email attachment functionality using Sparkpost. I get a generation failure in the logs on the sparkpost dashboard that indicates that my email's estimated size is more than 20 MB which is expected since I was testing that scenario.
However in the HTTP response I only receive
{{"total_rejected_recipients": 0,"total_accepted_recipients": 1,"id": "7099572646706409988"}}
I would like to know how I can get an error code or error in my response from sparkpost
My code looks something like this
HttpWebRequest Request = WebRequest.Create(requestURL) as HttpWebRequest;
Request.Proxy = null;
Request.Method = ServiceRequestType.POST.ToString();
AttachHeaders(headers, ref Request);
AttachTimeout(timeoutInSeconds, ref Request);
AttachContentType(contentType, ref Request);
AttachNetworkCredentials(credentials, ref Request);
AttachInputObject(content, ref Request);
Response = (HttpWebResponse)Request.GetResponse();
if ((Response.StatusCode == HttpStatusCode.OK || Response.StatusCode == HttpStatusCode.Accepted || Response.StatusCode == HttpStatusCode.Created || Response.StatusCode == HttpStatusCode.NoContent) == false)
{
throw new Exception(String.Format("Server error (HTTP {0}: {1}).", Response.StatusCode, Response.StatusDescription));
}
using (Response)
{
using (StreamReader ResponseReader = new StreamReader(Response.GetResponseStream()))
{
JsonResponse = JsonConvert.DeserializeObject(ResponseReader.ReadToEnd());
ResponseReader.Close();
}
Response.Close();
}
The logic for creating email is fine since I am able to send and recieve emails when the attachment size is within limits.