Merge pull request #1698 from ucb-bar/py3_fix

replace-content.py should use python3 explicitly

scripts/replace-content.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 # Replace text in a file given a key identifying a block to replace.
 # If the file doesn't exist, create it.