MAINT: remove python 3.4 branch (#1061)

Author: Carreau

jupyter_server/base/zmqhandlers.py

@@ -4,7 +4,6 @@
 import json
 import re
 import struct
-import sys
 from typing import Optional, no_type_check
 from urllib.parse import urlparse
 
@@ -42,8 +41,6 @@ def serialize_binary_message(msg):
     # don't modify msg or buffer list in-place
     msg = msg.copy()
     buffers = list(msg.pop("buffers"))
-    if sys.version_info < (3, 4):
-        buffers = [x.tobytes() for x in buffers]
     bmsg = json.dumps(msg, default=json_default).encode("utf8")
     buffers.insert(0, bmsg)
     nbufs = len(buffers)