cros_build_lib.run: clean up combine_stdout_stderr->stderr migration

BUG=chromium:1006587
TEST=`./run_tests` passes

Change-Id: I813459822507840e9c57f1891fbf067573b5e7df
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/1972672
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Chris McDonald <cjmcdonald@chromium.org>
diff --git a/scripts/cros_sdk_unittest.py b/scripts/cros_sdk_unittest.py
index d2632ac..a3f48d7 100644
--- a/scripts/cros_sdk_unittest.py
+++ b/scripts/cros_sdk_unittest.py
@@ -8,6 +8,7 @@
 from __future__ import print_function
 
 import os
+import subprocess
 import unittest
 
 from chromite.lib import cros_build_lib
@@ -119,7 +120,7 @@
     try:
       result = cros_build_lib.run(
           cmd, print_cmd=False, capture_output=True, check=False,
-          combine_stdout_stderr=True)
+          stderr=subprocess.STDOUT)
     except cros_build_lib.RunCommandError as e:
       raise SystemExit('Running %r failed!: %s' % (cmd, e))