bpo-29446: IDLE -- add explicit imports (GH-14919)

Stop depending on tkinter import *.
diff --git a/Lib/idlelib/editor.py b/Lib/idlelib/editor.py
index 497ee12..35027da 100644
--- a/Lib/idlelib/editor.py
+++ b/Lib/idlelib/editor.py
@@ -2,7 +2,9 @@
 import importlib.util
 import os
 import platform
+import re
 import string
+import sys
 import tokenize
 import traceback
 import webbrowser