style: some of the suggestions from flake8
diff --git a/serial/urlhandler/protocol_socket.py b/serial/urlhandler/protocol_socket.py
index 7932ee0..2f01a4a 100644
--- a/serial/urlhandler/protocol_socket.py
+++ b/serial/urlhandler/protocol_socket.py
@@ -16,6 +16,7 @@
 # options:
 # - "debug" print diagnostic messages
 
+import errno
 import logging
 import select
 import socket