include content-length to error response

src/server/error.rs

@@ -16,11 +16,12 @@ impl HttpHandlerTask for ServerError {
     fn poll_io(&mut self, io: &mut Writer) -> Poll<bool, Error> {
         {
             let bytes = io.buffer();
-            //Buffer should have sufficient capacity for status line
-            //and extra space
+            // Buffer should have sufficient capacity for status line
+            // and extra space
             bytes.reserve(helpers::STATUS_LINE_BUF_SIZE + 1);
             helpers::write_status_line(self.0, self.1.as_u16(), bytes);
         }
+        io.buffer().extend_from_slice(b"\r\ncontent-length: 0\r\n");
         io.set_date();
         Ok(Async::Ready(true))
     }