where '%s' is replaced with app_or_project and extensions joined into a string, separated by a string ', '. call the method self.stdout.write, with an argument string "Rendering %s template files with filenames: %s\n",
self . stdout . write ( "Rendering %s template files with " "filenames: %s\n" % ( app_or_project , ', ' . join ( extra_files ) ) )