"'NoneType' is not callable" error when running smile.py

[peymanmortazavi]

Running the following command causes the following error.

$ python smile.py
Using TensorFlow backend.

wandb: wandb dryrun mode. Use "wandb run <script>" to save results to wandb.
wandb: Run directory: wandb/dryrun-20171101_232123-fpcy4wnv

/home/peyman.mortazavi/.envs/class/lib/python3.4/site-packages/keras/models.py:848: UserWarning: The nb_epoch argument in fit has been renamed epochs.
warnings.warn('The nb_epoch argument in fit '
Train on 11848 samples, validate on 1317 samples
Epoch 1/3
2017-11-01 23:21:30.392279: W tensorflow/core/platform/cpu_feature_guard.cc:45] The TensorFlow library wasn't compiled to use SSE4.1 instructions, but these are available on your machine and could speed up CPU computations.
2017-11-01 23:21:30.392322: W tensorflow/core/platform/cpu_feature_guard.cc:45] The TensorFlow library wasn't compiled to use SSE4.2 instructions, but these are available on your machine and could speed up CPU computations.
2017-11-01 23:21:30.392334: W tensorflow/core/platform/cpu_feature_guard.cc:45] The TensorFlow library wasn't compiled to use AVX instructions, but these are available on your machine and could speed up CPU computations.
2017-11-01 23:21:30.392342: W tensorflow/core/platform/cpu_feature_guard.cc:45] The TensorFlow library wasn't compiled to use AVX2 instructions, but these are available on your machine and could speed up CPU computations.
2017-11-01 23:21:30.392350: W tensorflow/core/platform/cpu_feature_guard.cc:45] The TensorFlow library wasn't compiled to use FMA instructions, but these are available on your machine and could speed up CPU computations.
11848/11848 [==============================] - 31s - loss: 0.5208 - acc: 0.7261 - val_loss: 0.4176 - val_acc: 0.7715
Epoch 2/3
11848/11848 [==============================] - 28s - loss: 0.3844 - acc: 0.8390 - val_loss: 0.3714 - val_acc: 0.8679
Epoch 3/3
11848/11848 [==============================] - 28s - loss: 0.3511 - acc: 0.8688 - val_loss: 0.3096 - val_acc: 0.8884
Exception ignored in: <bound method Session.del of <tensorflow.python.client.session.Session object at 0x7fcfb5b92eb8>>
Traceback (most recent call last):
File "/home/peyman.mortazavi/.envs/class/lib/python3.4/site-packages/tensorflow/python/client/session.py", line 701, in del
TypeError: 'NoneType' object is not callable