The error message you’re seeing suggests that the file system you’re trying to write to is read-only. This could be caused by a number of things, including file permissions or issues with the disk itself. 

One possible workaround for installing new editor themes in JupyterLab is to use a different directory that isn’t read-only. You can specify a custom directory for installing packages using the --user flag when running pip install. For example: 

pip install --user jupyterlab-theme 

This will install the “jupyterlab-theme” package in your home directory rather than the global site-packages directory, which should bypass any issues with read-only file systems. 

You can try running JupyterLab as an administrator using "sudo" on Linux/Mac or running as Administrator on Windows, if you have permission. This can sometimes resolve issues with file permissions. 

I hope this helps! Let me know if you have any other questions.