Unresponsive Jupyterhub
Problem: Jupyterhub occasionally becomes unresponsive, the browser displays "A web page is slowing down your browser, what would you like to do? Stop it/Wait".
It has to do with Jupyterhub trying to update a git repository every few minutes. This seems to happen automatically if the working directory contains a .git subfolder. If the working directory contains a lot of data (which may happen if you stop versioning a project, forget about it, and keep saving stuff in the same place), then jupyterhub becomes unresponsive.
Solution: List any subdirs with large amounts of data in .gitignore.