ValueError: Variable rnn/basic_rnn_cell/kernel already exists, disallowed. Did you mean to set reuse=True or reuse=tf.AUTO_REUSE in VarScope?
Does this happen when you run the model for the first time (upon opening a new python console)?
If not, you need to clear you computational graph. You can do that by putting this line at the beginning of your script.
tf.reset_default_graph()