title: Unable to save model weights
body: <p>Has anyone ever seen this error message: </p>
  
  <pre><code>OSError: Unable to create file (unable to open file: name = './snapshots/resnet50_csv_01.h5', errno = 2, error message = 'No such file or directory', flags = 13, o_flags = 242)
  </code></pre>
  
  <p>I am unsure what I am doing wrong. </p>
  
  <p>Full: </p>
  
  <pre><code>  Epoch 00001: saving model to ./snapshots/resnet50_csv_01.h5
  Traceback (most recent call last):
    File "../keras-retinanet-0.1/keras_retinanet/bin/train.py", line 264, in &lt;module&gt;
      main()
    File "../keras-retinanet-0.1/keras_retinanet/bin/train.py", line 260, in main
      callbacks=callbacks,
    File "/gpfs0/users/lindgren/pstrain/virtual_enviroments/final_placenta_virtual_enviroment/lib/python3.6/site-packages/keras/legacy/interfaces.py", line 91, in wrapper
      return func(*args, **kwargs)
    File "/gpfs0/users/lindgren/pstrain/virtual_enviroments/final_placenta_virtual_enviroment/lib/python3.6/site-packages/keras/engine/training.py", line 1415, in fit_generator
      initial_epoch=initial_epoch)
    File "/gpfs0/users/lindgren/pstrain/virtual_enviroments/final_placenta_virtual_enviroment/lib/python3.6/site-packages/keras/engine/training_generator.py", line 247, in fit_generator
      callbacks.on_epoch_end(epoch, epoch_logs)
    File "/gpfs0/users/lindgren/pstrain/virtual_enviroments/final_placenta_virtual_enviroment/lib/python3.6/site-packages/keras/callbacks.py", line 77, in on_epoch_end
      callback.on_epoch_end(epoch, logs)
    File "../keras-retinanet-0.1/keras_retinanet/bin/../../keras_retinanet/callbacks/common.py", line 30, in on_epoch_end
      self.callback.on_epoch_end(epoch, logs=logs)
    File "/gpfs0/users/lindgren/pstrain/virtual_enviroments/final_placenta_virtual_enviroment/lib/python3.6/site-packages/keras/callbacks.py", line 455, in on_epoch_end
      self.model.save(filepath, overwrite=True)
    File "/gpfs0/users/lindgren/pstrain/virtual_enviroments/final_placenta_virtual_enviroment/lib/python3.6/site-packages/keras/engine/network.py", line 1085, in save
      save_model(self, filepath, overwrite, include_optimizer)
    File "/gpfs0/users/lindgren/pstrain/virtual_enviroments/final_placenta_virtual_enviroment/lib/python3.6/site-packages/keras/engine/saving.py", line 105, in save_model
      f = h5py.File(filepath, mode='w')
    File "/gpfs0/users/lindgren/pstrain/virtual_enviroments/final_placenta_virtual_enviroment/lib/python3.6/site-packages/h5py/_hl/files.py", line 312, in __init__
      fid = make_fid(name, mode, userblock_size, fapl, swmr=swmr)
    File "/gpfs0/users/lindgren/pstrain/virtual_enviroments/final_placenta_virtual_enviroment/lib/python3.6/site-packages/h5py/_hl/files.py", line 148, in make_fid
      fid = h5f.create(name, h5f.ACC_TRUNC, fapl=fapl, fcpl=fcpl)
    File "h5py/_objects.pyx", line 54, in h5py._objects.with_phil.wrapper
    File "h5py/_objects.pyx", line 55, in h5py._objects.with_phil.wrapper
    File "h5py/h5f.pyx", line 98, in h5py.h5f.create
  OSError: Unable to create file (unable to open file: name = './snapshots/resnet50_csv_01.h5', errno = 2, error message = 'No such file or directory', flags = 13, o_flags = 242)
  </code></pre>