plotly.py: jsonschema.SchemaError when a figure is validated

Here is a minimal example that reproduces the bug: http://nbviewer.jupyter.org/gist/empet/cf922d7c7f4269d6f63432ec67a5d020

The notebook runs OK (with plotly 2.0.1) when I call plot(fig). iplot(fig) generates the plot too, but an error box pops up whenever Jupyter tries to save the notebook. The box has the following content:

The save operation succeeded, but the notebook does not appear to be valid. The validation error was: Notebook Validation failed: u'data': [{u'colorscale': u'Viridis', u'z': [[2, 27, 105, 100], [87, 14, 121, 102], [26, 121, 73, 34], [44, 105, 111, 127]], u'type': u'heatmap', u'zsmooth': u'best'}], u'layout': {u'width': 400, u'height': 400}} is not valid under any of the given schemas:

{ "data": [ { "colorscale": "Viridis", "z": [ [ 2, 27, 105, 100 ], [ 87, 14, 121, 102 ], [ 26, 121, 73, 34 ], [ 44, 105, 111, 127 ] ], "type": "heatmap", "zsmooth": "best" } ], "layout": { "width": 400, "height": 400 } }

Initially I formulated this issue only for heatmaps, but meanwhile I realized that this behaviour manifests for any type of plot.