Notebook save failure

[juhasch]

I can't save my notebook on master branch, if it contains this cell:

from IPython.display import Latex
display(Latex([1]))

I know Latex() should not be called like this, still this probably should not lead to a failure in saving the notebook.

[takluyver]

Here's the error trying to save this:

2013-11-20 11:21:23.228 [NotebookApp] ERROR | Unhandled error in API request
Traceback (most recent call last):
  File "/home/takluyver/.local/lib/python3.3/site-packages/IPython/html/base/handlers.py", line 276, in wrapper
    result = method(self, *args, **kwargs)
  File "/home/takluyver/.local/lib/python3.3/site-packages/IPython/html/services/notebooks/handlers.py", line 197, in put
    self._save_notebook(model, path, name)
  File "/home/takluyver/.local/lib/python3.3/site-packages/IPython/html/services/notebooks/handlers.py", line 133, in _save_notebook
    model = self.notebook_manager.save_notebook_model(model, name, path)
  File "/home/takluyver/.local/lib/python3.3/site-packages/IPython/html/services/notebooks/filenbmanager.py", line 238, in save_notebook_model
    nb = current.to_notebook_json(model['content'])
  File "/home/takluyver/.local/lib/python3.3/site-packages/IPython/nbformat/v3/nbjson.py", line 49, in to_notebook
    return rejoin_lines(from_dict(d))
  File "/home/takluyver/.local/lib/python3.3/site-packages/IPython/nbformat/v3/rwbase.py", line 85, in rejoin_lines
    output[key] = _join_lines(item)
  File "/home/takluyver/.local/lib/python3.3/site-packages/IPython/nbformat/v3/rwbase.py", line 58, in _join_lines
    if lines and lines[0].endswith(('\n', '\r')):
AttributeError: 'int' object has no attribute 'endswith'

Either the classes, or the display protocol, or both, should probably be rejecting the data being provided as something that's not a string.

[takluyver]

@minrk is going to add checks in various places

[juhasch]

Thanks for looking into this. @minrk : The new checks work for me.