py23 import in all nontrivial source files and unused import cleanup
diff --git a/Lib/fontTools/ttLib/sfnt.py b/Lib/fontTools/ttLib/sfnt.py
index 136dde3..a194d77 100644
--- a/Lib/fontTools/ttLib/sfnt.py
+++ b/Lib/fontTools/ttLib/sfnt.py
@@ -12,10 +12,9 @@
 a table's length chages you need to rewrite the whole file anyway.
 """
 
-import sys
 import struct
-import os
 from fontTools.misc import sstruct
+from fontTools.misc.py23 import *
 
 
 class SFNTReader: