Backtrace on `ipython notebook Alanine\ Example.ipynb

gistfile1.txt

Wigner:~/Downloads/tmp dwhs$ ipython nbconvert Alanine\ Example.ipynb
[NbConvertApp] Using existing profile dir: u'/Users/dwhs/.ipython/profile_default'
[NbConvertApp] Converting notebook Alanine Example.ipynb to html
[NbConvertApp] Support files will be in Alanine Example_files/
Traceback (most recent call last):
  File "/opt/local/bin/ipython", line 5, in <module>
    start_ipython()
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/__init__.py", line 120, in start_ipython
    return launch_new_instance(argv=argv, **kwargs)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/config/application.py", line 564, in launch_instance
    app.start()
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/terminal/ipapp.py", line 367, in start
    return self.subapp.start()
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/nbconvert/nbconvertapp.py", line 268, in start
    self.convert_notebooks()
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/nbconvert/nbconvertapp.py", line 301, in convert_notebooks
    output, resources = exporter.from_filename(notebook_filename, resources=resources)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/nbconvert/exporters/exporter.py", line 151, in from_filename
    return self.from_notebook_node(nbformat.read(f, 'json'), resources=resources, **kw)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/nbconvert/exporters/templateexporter.py", line 209, in from_notebook_node
    nb_copy, resources = super(TemplateExporter, self).from_notebook_node(nb, resources, **kw)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/nbconvert/exporters/exporter.py", line 123, in from_notebook_node
    nb_copy, resources = self._preprocess(nb_copy, resources)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/nbconvert/exporters/exporter.py", line 274, in _preprocess
    nbc, resc = preprocessor(nbc, resc)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/nbconvert/preprocessors/coalescestreams.py", line 31, in wrappedfunc
    worksheet.cells[index], resources = function(cell, resources, index)
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/nbconvert/preprocessors/coalescestreams.py", line 73, in coalesce_streams
    if output.output_type == 'stream' and '\r' in output.text:
  File "/opt/local/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/IPython/utils/ipstruct.py", line 149, in __getattr__
    raise AttributeError(key)
AttributeError: output_type

I am confused, what does this mean? Is there something strange in the notebook, that cannot be converted?