FileNotFoundError possible when displaying images

[datakurre]

  File "/home/datakurre/robotlab/lib/python3.6/site-packages/robotkernel/executors.py", line 291, in run_robot_suite
    bundle, metadata = to_mime_and_metadata(return_values[-1])
  File "/home/datakurre/robotlab/lib/python3.6/site-packages/robotkernel/utils.py", line 192, in to_mime_and_metadata
    return Image(obj, embed=True)._repr_mimebundle_()
  File "/home/datakurre/robotlab/lib/python3.6/site-packages/IPython/core/display.py", line 1262, in _repr_mimebundle_
    data, metadata = self._data_and_metadata(always_both=True)
  File "/home/datakurre/robotlab/lib/python3.6/site-packages/IPython/core/display.py", line 1275, in _data_and_metadata
    "No such file or directory: '%s'" % (self.data))
FileNotFoundError: No such file or directory: 'None'