Add intlist_to_bytes to utils.py

youtube_dl/utils.py

@@ -718,3 +718,10 @@ def bytes_to_intlist(bs):
     else:
         return [ord(c) for c in bs]
 
+def intlist_to_bytes(xs):
+    if not xs:
+        return b''
+    if isinstance(chr(0), bytes):  # Python 2
+        return ''.join([chr(x) for x in xs])
+    else:
+        return bytes(xs)