Fix broken git tests on mac.

git_common.py

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Monkeypatch IMapIterator so that Ctrl-C can kill everything properly.
 # Derived from https://gist.github.com/aljungberg/626518
 import multiprocessing.pool
 from multiprocessing.pool import IMapIterator
 def wrapper(func):
   def wrap(self, timeout=None):
@@ skipping 738 matching lines @@
   run('config', '--' + scope, option, value)
 
 
 def get_dirty_files():
   # Make sure index is up-to-date before running diff-index.
   run_with_retcode('update-index', '--refresh', '-q')
   return run('diff-index', '--name-status', 'HEAD')
 
 
 def is_dirty_git_tree(cmd):
+  w = lambda s: sys.stderr.write(s+"\n")
+
   dirty = get_dirty_files()
   if dirty:
-    print 'Cannot %s with a dirty tree. '\
-          'Commit, freeze or stash your changes first.' % cmd
-    print 'Uncommitted files: (git diff-index --name-status HEAD)'
-    print dirty[:4096]
+    w('Cannot %s with a dirty tree. Commit, freeze or stash your changes first.'
+      % cmd)
+    w('Uncommitted files: (git diff-index --name-status HEAD)')
+    w(dirty[:4096])
     if len(dirty) > 4096: # pragma: no cover
-      print '... (run "git diff-index --name-status HEAD" to see full output).'
+      w('... (run "git diff-index --name-status HEAD" to see full output).')
     return True
   return False
 
 
 def status():
   """Returns a parsed version of git-status.
 
   Returns a generator of (current_name, (lstat, rstat, src)) pairs where:
     * current_name is the name of the file
     * lstat is the left status code letter from git-status
@@ skipping 234 matching lines @@
                       ['HEAD'])
 
 
 def clone_file(repository, new_workdir, link, operation):
   if not os.path.exists(os.path.join(repository, link)):
     return
   link_dir = os.path.dirname(os.path.join(new_workdir, link))
   if not os.path.exists(link_dir):
     os.makedirs(link_dir)
   operation(os.path.join(repository, link), os.path.join(new_workdir, link))