Used app_label instead of appname.

The last component of the dotted path to the application module is
consistently referenced as the application "label". For instance it's
AppConfig.label. appname could be confused with AppConfig.name, which is
the full dotted path.

tests/admin_scripts/management/commands/app_command.py

@@ -4,7 +4,7 @@ from django.core.management.base import AppCommand
 class Command(AppCommand):
     help = 'Test Application-based commands'
     requires_model_validation = False
-    args = '[appname ...]'
+    args = '[app_label ...]'
 
     def handle_app_config(self, app_config, **options):
         print('EXECUTE:AppCommand name=%s, options=%s' % (app_config.name, sorted(options.items())))