Set up issues.

In a newly created environment the following is not a recognized sub command:
`jupyter nbextension enable --py --sys-prefix widgetsnbextension`

Start by reproducing the reported command in a newly created environment: `jupyter nbextension enable --py --sys-prefix widgetsnbextension`. Check the repository's environment setup instructions and determine what should make this subcommand available. Done means the setup no longer produces the reported unrecognized-subcommand error.

Scritto dal modello di indicizzazione a partire dal testo della issue.