bugfix for rnn tutorial on Python3

tutorials/rnn/ptb/reader.py

@@ -25,10 +25,14 @@ import sys
 
 import tensorflow as tf
 
+Py3 = sys.version_info[0] == 3
 
 def _read_words(filename):
   with tf.gfile.GFile(filename, "r") as f:
-    return f.read().decode("utf-8").replace("\n", "<eos>").split()
+    if Py3:
+      return f.read().replace("\n", "<eos>").split()
+    else:
+      return f.read().decode("utf-8").replace("\n", "<eos>").split()
 
 
 def _build_vocab(filename):