refactor(http1): return Parse::Internal error if there's an illegal header name or value (#2544)

src/error.rs

@@ -73,6 +73,8 @@ pub(super) enum Parse {
     Header,
     TooLarge,
     Status,
+    #[cfg_attr(debug_assertions, allow(unused))]
+    Internal,
 }
 
 #[derive(Debug, PartialEq)]
@@ -374,6 +376,9 @@ impl Error {
             Kind::Parse(Parse::Header) => "invalid HTTP header parsed",
             Kind::Parse(Parse::TooLarge) => "message head is too large",
             Kind::Parse(Parse::Status) => "invalid HTTP status-code parsed",
+            Kind::Parse(Parse::Internal) => {
+                "internal error inside Hyper and/or its dependencies, please report"
+            }
             Kind::IncompleteMessage => "connection closed before message completed",
             #[cfg(feature = "http1")]
             Kind::UnexpectedMessage => "received unexpected message from connection",