Track update to ToT libxml2.

Change-Id: Idf5a11c607dc397721ec95846dc819f85a646c37
diff --git a/python/setup.py b/python/setup.py
index e504323..e1ff365 100755
--- a/python/setup.py
+++ b/python/setup.py
@@ -8,7 +8,7 @@
 # Below ROOT, we expect to find include, include/libxml2, lib and bin.
 # On *nix, it is not needed (but should not harm),
 # on Windows, it is set by configure.js.
-ROOT = r'/usr'
+ROOT = r'/usr/local'
 
 # Thread-enabled libxml2
 with_threads = 1