subprocess2.check_output() doesn't allow stdout, like python2.7's version.

Don't bother, but redirect stderr.

TBR=dpranke@chromium.org
BUG=
TEST=


Review URL: http://codereview.chromium.org/7865005

git-svn-id: svn://svn.chromium.org/chrome/trunk/tools/depot_tools@100464 0039d316-1c4b-4281-b951-d872f2087c98

trychange.py

@@ -442,7 +442,7 @@ def GuessVCS(options, path):
   try:
     subprocess2.check_output(
         ['git', 'rev-parse', '--is-inside-work-tree'], cwd=real_path,
-        stdout=subprocess2.VOID)
+        stderr=subprocess2.VOID)
     return GIT(options, path)
   except subprocess2.CalledProcessError, e:
     if e.returncode != errno.ENOENT and e.returncode != 128: