convert shebang lines: python -> python3
diff --git a/Demo/zlib/minigzip.py b/Demo/zlib/minigzip.py
index 28d8b26..b2af7f9 100755
--- a/Demo/zlib/minigzip.py
+++ b/Demo/zlib/minigzip.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 # Demo program for zlib; it compresses or decompresses files, but *doesn't*
 # delete the original.  This doesn't support all of gzip's options.
 #