I don't use jupyter, so apologies if this is a daft question, but is this a virtualenvwrapper command to just install one specific package in the created virtualenv? That seems like a very narrow/specific use case, but maybe I've misunderstood?

Yes and no - with jupyter it's one thing to install the ipykernel module in a second environment, but many people stumble on the second bit, i.e. letting the main installation of jupyter know about the new environment. I would agree with you about it being a relatively narrow use case in terms of functionality, however it seems to me that the popularity of notebooks as a prototyping platform makes this a feature that would be useful to a lot of people. It would also encourage best practices in terms of:

• maintaining one installation of jupyter and installing the ipykernel in other environments, and
• creating separate environments for tasks / projects.

Thanks for considering the PR and I understand if this is not a direction in which you want to take the project.