def check_skipped_app_config(self):
        """Check for mounted Applications that have no config."""
        for sn, app in cherrypy.tree.apps.items():
            if not isinstance(app, cherrypy.Application):
                continue
            if not app.config:
                msg = 'The Application mounted at %r has an empty config.' % sn
                if self.global_config_contained_paths:
                    msg += (
                        ' It looks like the config you passed to '
                        'cherrypy.config.update() contains application-'
                        'specific sections. You must explicitly pass '
                        'application config via '
                        'cherrypy.tree.mount(..., config=app_config)'
                    )
                warnings.warn(msg)
                return
Check for mounted Applications that have no config.
cherrypy/_cpchecker.py