Fix a presubmit.py breakage on python 2.4

presubmit.py

 #!/usr/bin/python
 # Copyright (c) 2006-2009 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.
 
 """Enables directory-specific presubmit checks to run at upload and/or commit.
 """
 
 __version__ = '1.0.1'
 
@@ skipping 612 matching lines @@
   """
   presubmit_files = ListRelevantPresubmitFiles(change_info.FileList())
   if not presubmit_files and verbose:
     print "Warning, no presubmit.py found."
   results = []
   executer = PresubmitExecuter(change_info, committing)
   for filename in presubmit_files:
     if verbose:
       print "Running %s" % filename
     # Accept CRLF presubmit script.
-    presubmit_script = gcl.ReadFile(filename, 'Ur')
+    presubmit_script = gcl.ReadFile(filename, 'rU')
     results += executer.ExecPresubmitScript(presubmit_script, filename)
 
   errors = []
   notifications = []
   warnings = []
   for result in results:
     if not result.IsFatal() and not result.ShouldPrompt():
       notifications.append(result)
     elif result.ShouldPrompt():
       warnings.append(result)
@@ skipping 56 matching lines @@
     print "Found %d files." % len(files)
   return DoPresubmitChecks(gcl.ChangeInfo(name='temp', files=files),
                            options.commit,
                            options.verbose,
                            sys.stdout,
                            sys.stdin)
 
 
 if __name__ == '__main__':
   sys.exit(Main(sys.argv))