Revert "Change TestResultServer to use python 2.7."

Tools/TestResultServer/model/datastorefile.py

 # Copyright (C) 2010 Google Inc. All rights reserved.
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+from datetime import datetime
 import logging
 
 from google.appengine.ext import db
 
 MAX_DATA_ENTRY_PER_FILE = 10
 MAX_ENTRY_LEN = 1000 * 1000
 
 
 class DataEntry(db.Model):
     """Datastore entry that stores one segmant of file data
@@ skipping 101 matching lines @@
             data_entry = DataEntry.get(key)
             if not data_entry:
                 logging.error("No data found for key: %s.", key)
                 return None
 
             data.append(data_entry.data)
 
         self.data = "".join(data)
 
         return self.data