check_return_value.py should drop stderr of the command it runs.

build/check_return_value.py

Index: build/check_return_value.py
diff --git a/build/check_return_value.py b/build/check_return_value.py
index 6f0daec3a751bdf4f043274f1196193929b5dd4b..c659d1e9674ab96af49c3fb2dea8b061ecef162a 100755
--- a/build/check_return_value.py
+++ b/build/check_return_value.py
@@ -6,10 +6,12 @@
 """This program wraps an arbitrary command and prints "1" if the command ran
 successfully."""
 
+import os
 import subprocess
 import sys
 
-if not subprocess.call(sys.argv[1:]):
+devnull = open(os.devnull, 'wb')
+if not subprocess.call(sys.argv[1:], stdout=devnull, stderr=devnull):
   print 1
 else:
   print 0