fix default_url redirect when base_url is defined

as it is, when base_url is set, default_url would redirect to itself,
creating an infinite redirect loop.

The condition is meant to prevent this loop when the default_url is the base_url,
but base_url's default value was hardcoded in the check,
causing the behavior to only be correct when base_url has this default value.

Author: minrk

jupyter_server/serverapp.py

@@ -332,7 +332,7 @@ def init_handlers(self, default_services, settings):
         # register base handlers last
         handlers.extend(load_handlers('jupyter_server.base.handlers'))
 
-        if settings['default_url'] != '/':
+        if settings['default_url'] != settings['base_url']:
             # set the URL that will be redirected from `/`
             handlers.append(
                 (r'/?', RedirectWithParams, {