Actually, I think the chow could be squeezed into the previous mkdir command, ie, only `chown` if `mkdir`... 

```python
            root_cmd(
                '[ ! -d {0} ] && (mkdir -p {0}; chown 700 {0}; chown {1} {0}) || '
                'echo "Directory {0!r} already exists..."'.format(tmp_dir, username),
                tty, sudo, **kwargs
            )
```
No?