Display warning messages generated by nbconvert when exporting Notebooks

[DonJayamanne]

Furthermore, converting a notebook with nbconvert using vscode / plotly_mimetype will produce the following warning:

UserWarning: Your element with mimetype(s) dict_keys(['application/vnd.plotly.v1+json']) is not able to be represented.

It would be good if VS Code could produce a similar warning, if possbile, when trying to export application/vnd.plotly.v1+json content to HTML. Exporting to a static picture would of course be even more convenient.

See here #6999 (comment)

[DonJayamanne]

Closing this issue as no one has reported this anymore.