def METHOD_NAME(tmpdir, capsys):
    with chdir(tmpdir):
        with patch.object(docker, "APIClient") as client:
            client.side_effect = docker.errors.DockerException("Error: no Docker")
            app = Repo2Docker()
            with pytest.raises(SystemExit):
                app.build()
                captured = capsys.readouterr()
                assert "Error: no Docker" in captured.err