CommClosedError thrown by python script but not by IPython notebook

Hi

I get the following error if I run a `dask.distributed` script but no error when I run the same code in an IPython notebook:

```
tornado.application - ERROR - Exception in callback
Traceback (most recent call last):
File "/home/beowulf/miniconda2/envs/clarke/lib/python2.7/site-packages/tornado/ioloop.py", line 604, in _run_callback
ret = callback()
File "/home/beowulf/miniconda2/envs/clarke/lib/python2.7/site-packages/tornado/stack_context.py", line 275, in null_wrapper
return fn(*args, **kwargs)
File "/home/beowulf/miniconda2/envs/clarke/lib/python2.7/site-packages/distributed/batched.py", line 102, in send
raise CommClosedError
```

This is the code:

```
from distributed import Client

client = Client("127.0.0.1:8786")

def get_hostname():
import socket
return socket.gethostname()

def dummy(x):
return (get_hostname(), )

jobs = client.map(dummy, range(10000))
total = client.submit(len, jobs)
total.result()
```

I am guessing this is happening because the script terminates before the jobs do?

Any help would be gratefully received. Thanks.