Comment 3 for bug 1650481

I've got a password prompt warning / error just ahead a similar error message. Is that unrelated?

```
sudo: a password is required
2017-02-13 07:42:40 maasserver.regiondservices.ntp: [critical] Failed to update NTP configuration.
 Traceback (most recent call last):
   File "/usr/lib/python3.5/threading.py", line 862, in run
     self._target(*self._args, **self._kwargs)
   File "/usr/lib/python3/dist-packages/provisioningserver/utils/twisted.py", line 824, in worker
     return target()
   File "/usr/lib/python3/dist-packages/twisted/_threads/_threadworker.py", line 46, in work
     task()
   File "/usr/lib/python3/dist-packages/twisted/_threads/_team.py", line 190, in doWork
     task()
 --- <exception caught here> ---
   File "/usr/lib/python3/dist-packages/twisted/python/threadpool.py", line 246, in inContext
     result = inContext.theWork()
   File "/usr/lib/python3/dist-packages/twisted/python/threadpool.py", line 262, in <lambda>
     inContext.theWork = lambda: context.call(ctx, func, *args, **kw)
   File "/usr/lib/python3/dist-packages/twisted/python/context.py", line 118, in callWithContext
     return self.currentContext().callWithContext(ctx, func, *args, **kw)
   File "/usr/lib/python3/dist-packages/twisted/python/context.py", line 81, in callWithContext
     return func(*args,**kw)
   File "/usr/lib/python3/dist-packages/provisioningserver/utils/twisted.py", line 857, in callInContext
     return func(*args, **kwargs)
   File "/usr/lib/python3/dist-packages/provisioningserver/utils/twisted.py", line 225, in wrapper
     result = func(*args, **kwargs)
   File "/usr/lib/python3/dist-packages/provisioningserver/ntp/config.py", line 49, in configure
     mode=0o644)
   File "/usr/lib/python3/dist-packages/provisioningserver/utils/fs.py", line 281, in sudo_write_file
     raise ExternalProcessError(proc.returncode, command, stderr)
 provisioningserver.utils.shell.ExternalProcessError: Command `maas-rack atomic-write --filename /etc/ntp/maas.conf --mode 0644` returned non-zero exit status 1:
 None
```