private async Task TransformException(OwinContext context, ITransform transform, Exception ex)
{
string content = transform.GetContent(ex);
context.Response.ContentType = "text/plain";
context.Response.StatusCode = (int) transform.StatusCode;
context.Response.ReasonPhrase = transform.ReasonPhrase;
context.Response.ContentLength = content.Length;
await context.Response.WriteAsync(content);
}
