text: Title: Syntax error in nbgrader_config.py
  Body: Ran into an issue following the docs for using the assignment list with multiple courses
  
  My error coming up is
  
  Sep 10 07:03:34 bash: File "/etc/jupyter/nbgrader_config.py", line 2
  Sep 10 07:03:34 bash: from nbgrader.auth JupyterHubAuthPlugin
  Sep 10 07:03:34 bash: ^
  Sep 10 07:03:34 bash: SyntaxError: invalid syntax
  Sep 10 07:03:34 bash: [NbGrader | ERROR] Exception while loading config file /etc/jupyter/nbgrader_config.py
  
  I took the config from  Can I use the “Assignment List” extension with multiple classes? 
  
  from nbgrader.auth JupyterHubAuthPlugin
  c = get_config()
  c.Exchange.path_includes_course = True
  c.Authenticator.plugin_class = JupyterHubAuthPlugin
  
  Im stuck here becuase my multiclass is not working correctly and all users can see all assignments