Index: process.py
===================================================================
--- process.py	(revision 11704)
+++ process.py	(working copy)
@@ -265,8 +265,10 @@
             traceback.print_exc()
         finally:
             util.info('process exiting with exitcode %d' % exitcode)
-            sys.stdout.flush()
-            sys.stderr.flush()
+            if sys.stdout is not None:
+                sys.stdout.flush()
+            if sys.stderr is not None:
+                sys.stderr.flush()
 
         return exitcode