lesson learned don't put "venv" in your book folder.

[martinlarsalbert]

I want to report a problem I encountered with its cause and solution, so that someone else avoids it.
I don't know if this is a bug or just a trouble shot example. Please advice if this is a bug or just a trouble shoot example and how it then should be documented so that newbies like me avoid this mistake...?

I kept getting the following error when I was building my book (jb build book):
nbformat.validator.NotebookValidationError:` 'name' is a required property

I thought that one of my content notebooks was causing this, but when I remove all notebooks from _toc.yml the error remained.

As it turned out I had put a python environment folder "venv" in my book folder. When I moved it, the error dissapeared.

So lesson learned don't put "venv" in your book folder.