Fix automatic detection when git is not installed

trychange.py

 #!/usr/bin/env python
 # Copyright (c) 2011 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.
 
 """Client-side script to send a try job to the try server. It communicates to
 the try server by either writting to a svn repository or by directly connecting
 to the server by HTTP.
 """
 
@@ skipping 441 matching lines @@
   if os.path.isdir(os.path.join(real_path, '.svn')):
     return SVN(options, path, file_list)
 
   # Git has a command to test if you're in a git tree.
   # Try running it, but don't die if we don't have git installed.
   try:
     subprocess2.check_output(
         ['git', 'rev-parse', '--is-inside-work-tree'], cwd=real_path,
         stderr=subprocess2.VOID)
     return GIT(options, path, file_list)
+  except OSError, e:
+    if e.errno != errno.ENOENT:
+      raise
   except subprocess2.CalledProcessError, e:
     if e.returncode != errno.ENOENT and e.returncode != 128:
       # ENOENT == 2 = they don't have git installed.
       # 128 = git error code when not in a repo.
       logging.warning('Unexpected error code: %s' % e.returncode)
       raise
   raise NoTryServerAccess("Could not guess version control system. "
                           "Are you in a working copy directory?")
 
 
@@ skipping 339 matching lines @@
     return 1
   except (gclient_utils.Error, subprocess2.CalledProcessError), e:
     print >> sys.stderr, e
     return 1
   return 0
 
 
 if __name__ == "__main__":
   fix_encoding.fix_encoding()
   sys.exit(TryChange(None, None, False))