git-cl: Make tests run on Python 3.

Bug: 1002209
Change-Id: I90de660afd901e544e5557f3af3a56cef4d6adaf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/1891667
Commit-Queue: Edward Lesmes <ehmaldonado@chromium.org>
Reviewed-by: Anthony Polito <apolito@google.com>
diff --git a/git_cl.py b/git_cl.py
index 9f8e61c..af4b843 100755
--- a/git_cl.py
+++ b/git_cl.py
@@ -811,13 +811,9 @@
   if 'GIT_EXTERNAL_DIFF' in env:
     del env['GIT_EXTERNAL_DIFF']
 
-  try:
-    stdout = sys.stdout.fileno()
-  except AttributeError:
-    stdout = None
   return subprocess2.call(
       ['git', 'diff', '--no-ext-diff', '--stat', '-l100000', '-C50'] + args,
-      stdout=stdout, env=env)
+      env=env)
 
 
 class BuildbucketResponseException(Exception):