One of our dependencies is jupyterlab-widgets. When updating the conda-forge feedstock, I also added the dependency in the recipe, but that failed to build. So it looks like it's not strictly needed?

So ...

• Is it necessary?
• Does having it as a dependency force users to install jupyterlab even if they don't use it?
• If users do use jupyterlab, and we would not list this dependency, would jupyter-rfb fail?