[3899] Added code promotion before output

src/lib/dns/opcode.cc

@@ -50,7 +50,8 @@ const uint8_t MAX_OPCODE = 15;
 Opcode::Opcode(const uint8_t code) : code_(static_cast<CodeValue>(code)) {
     if (code > MAX_OPCODE) {
         isc_throw(OutOfRange,
-                  "DNS Opcode is too large to construct: " << code);
+                  "DNS Opcode is too large to construct: "
+		  << static_cast<unsigned>(code));
     }
 }