"None" appears when converting to HTML with "full" template

[alimanfoo]

When I use jupyter nbconvert --to html --template full I get an HTML file which looks great, apart from the fact that the text "None" appears at the top of the page. Looking at the HTML source, the text "None" is right at the beginning, before the doctype declaration.

To reproduce, run:

jupyter nbconvert --to html --template full any.ipynb

If instead of --template full I use --template classic this problem goes away. I gather that --template classic is now preferred, but the help docs still mention using --template full.

Seems to happen with pretty much any notebook.

Nbconvert version: 6.2.0

[MSeal]

We've had full deprecated for several versions. At this point we should just remove it from nbconvert. Thank you for updating the docs.