...subprocess will do the right thing given simply 'unbound' here because we split the command string into a list.

```python
>>> subprocess.Popen("echo ok".split())
<subprocess.Popen object at 0x104dddb10>
>>> ok

>>> subprocess.Popen("echo ok")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/Cellar/python/2.7.3/lib/python2.7/subprocess.py", line 679, in __init__
    errread, errwrite)
  File "/usr/local/Cellar/python/2.7.3/lib/python2.7/subprocess.py", line 1249, in _execute_child
    raise child_exception
OSError: [Errno 2] No such file or directory
```