text: Title: Error during notebook initialization. argument of type 'WindowsPath' is not iterable.
  Body: From email from user:
  
  > When trying to “watch” a notebook, the following error occurs: Error during notebook initialization. argument of type 'WindowsPath' is not iterable.
  
  > Somewhere in the settings.py file (mercury). A string was expected, but a path was provided.
  
  > I cast all  x / “y” to str(x / “y”) e.g. STATIC_ROOT = str(BASE_DIR / "static").
  
  > This seemed to fix the error.