convert to print_function

BUG=chromium:414895
TEST=`./cbuildbot/run_tests` passes
TEST=`cros lint` passes (it complains if print is used incorrectly)
TEST=`cbuildbot chromiumos-sdk` passes
TEST=`cbuildbot lumpy-release` passes

Change-Id: I67e7e1290b03a16525e0c2b1afa74ebbd8d3508f
Reviewed-on: https://chromium-review.googlesource.com/218572
Reviewed-by: David James <davidjames@chromium.org>
Reviewed-by: Yu-Ju Hong <yjhong@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
diff --git a/scripts/cros.py b/scripts/cros.py
index 8d49d04..4d9e184 100644
--- a/scripts/cros.py
+++ b/scripts/cros.py
@@ -13,6 +13,8 @@
 See cros/command/cros_XXX.py for actual command implementations.
 """
 
+from __future__ import print_function
+
 import sys
 
 from chromite.cros import commands