convert shebang lines: python -> python3
diff --git a/Tools/scripts/checkappend.py b/Tools/scripts/checkappend.py
index 4c74ee5..caa85db 100755
--- a/Tools/scripts/checkappend.py
+++ b/Tools/scripts/checkappend.py
@@ -1,4 +1,4 @@
-#! /usr/bin/env python
+#! /usr/bin/env python3
 
 # Released to the public domain, by Tim Peters, 28 February 2000.