change missed calls to fail_image_name() into fail invalid_argument('image_name')
change missed calls to fail_image_name() into fail invalid_argument('image_name')

cyber-dojo/runner_stateless,cyber-dojo/runner,cyber-dojo/runner_stateless,cyber-dojo/runner_stateless,cyber-dojo/runner_stateless,cyber-dojo/runner_stateless,cyber-dojo/runner,cyber-dojo/runner_stateless,cyber-dojo/runner_stateless