Fix import in release script

Change-Id: I47a2185c0a4b486ee4b777e4cc75f880496e71b6
diff --git a/tools/r8_release.py b/tools/r8_release.py
index cc4bebd..3e743b3 100755
--- a/tools/r8_release.py
+++ b/tools/r8_release.py
@@ -10,7 +10,7 @@
 import subprocess
 import sys
 import urllib
-import xml
+import xml.etree.ElementTree
 import zipfile
 
 import utils