import sys before we use it on line 9 (#828)

Lib/idlelib/pyshell.py

 #! /usr/bin/env python3
 
+import sys
+
 try:
     from tkinter import *
 except ImportError:
@@ -25,7 +27,6 @@ from platform import python_version, system
 import re
 import socket
 import subprocess
-import sys
 import threading
 import time
 import tokenize