py3: update check_boot_jars

Change-Id: I71ba943fb8c23713efc7c2a815fd2ddb9fa659f2
diff --git a/core/tasks/check_boot_jars/check_boot_jars.py b/core/tasks/check_boot_jars/check_boot_jars.py
index 5a0ec40..cd0bd75 100755
--- a/core/tasks/check_boot_jars/check_boot_jars.py
+++ b/core/tasks/check_boot_jars/check_boot_jars.py
@@ -1,5 +1,7 @@
 #!/usr/bin/env python
 
+from __future__ import print_function
+
 """
 Check boot jars.
 
@@ -55,15 +57,15 @@
       package_name = package_name.replace('/', '.')
       # Skip class without a package name
       if package_name and not whitelist_re.match(package_name):
-        print >> sys.stderr, ('Error: %s: unknown package name of class file %s'
-                              % (jar, f))
+        print('Error: %s: unknown package name of class file %s'
+              % (jar, f), file=sys.stderr)
         return False
   return True
 
 
 def main(argv):
   if len(argv) < 2:
-    print __doc__
+    print(__doc__)
     return 1
 
   if not LoadWhitelist(argv[0]):