Use hashlib module instead of md5 if it is present.

tools/presubmit.py

 #!/usr/bin/env python
 #
 # Copyright 2008 the V8 project authors. All rights reserved.
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 # modification, are permitted provided that the following conditions are
 # met:
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 #       with the distribution.
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 #       from this software without specific prior written permission.
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 # SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 # LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+try:
+  import hashlib
+  md5er = hashlib.md5
+except ImportError, e:
+  import md5
+  md5er = md5.new
 
-import md5
+
 import optparse
 import os
 from os.path import abspath, join, dirname, basename, exists
 import pickle
 import re
 import sys
 import subprocess
 
 # Disabled LINT rules and reason.
 # build/include_what_you_use: Started giving false positives for variables
@@ skipping 77 matching lines @@
       sums_file = open(self.sums_file_name, 'w')
       pickle.dump(self.sums, sums_file)
     finally:
       sums_file.close()
 
   def FilterUnchangedFiles(self, files):
     changed_or_new = []
     for file in files:
       try:
         handle = open(file, "r")
-        file_sum = md5.new(handle.read()).digest()
+        file_sum = md5er(handle.read()).digest()
         if not file in self.sums or self.sums[file] != file_sum:
           changed_or_new.append(file)
           self.sums[file] = file_sum
       finally:
         handle.close()
     return changed_or_new
 
   def RemoveFile(self, file):
     if file in self.sums:
       self.sums.pop(file)
@@ skipping 150 matching lines @@
     success = CppLintProcessor().Run(workspace) and success
   success = SourceProcessor().Run(workspace) and success
   if success:
     return 0
   else:
     return 1
 
 
 if __name__ == '__main__':
   sys.exit(Main())