cmd_utils - Import PIPE to this namespace

So users don't need to import subprocess again just for PIPE.

TEST=Run related tests on link
BUG=None

Change-Id: Id891dda00eb0c6d208d7390b1bb6534a61374b12
Reviewed-on: https://chromium-review.googlesource.com/180392
Reviewed-by: Hsinyu Chao <hychao@chromium.org>
Commit-Queue: Owen Lin <owenlin@chromium.org>
Tested-by: Owen Lin <owenlin@chromium.org>
diff --git a/client/cros/audio/sox_utils.py b/client/cros/audio/sox_utils.py
index 22a5fd7..693ef4d 100644
--- a/client/cros/audio/sox_utils.py
+++ b/client/cros/audio/sox_utils.py
@@ -4,7 +4,6 @@
 
 import logging
 import re
-import subprocess
 
 from autotest_lib.client.cros.audio import cmd_utils
 
@@ -132,7 +131,7 @@
     It returns the statistical information (in text) read from the standard
     error.
     """
-    p = cmd_utils.popen(stat_cmd(*args, **kargs), stderr=subprocess.PIPE)
+    p = cmd_utils.popen(stat_cmd(*args, **kargs), stderr=cmd_utils.PIPE)
 
     #The output is read from the stderr instead of stdout
     stat_output = p.stderr.read()