Arch distro fails to write network config with empty dns-nameservers

In distros/arch.py, the network configuration is created using

'DNS': str(tuple(info.get('dns-nameservers'))).replace(',', '')

However, when dns-nameservers is None, this causes both cloud-init and cloud-init-local to fail with

failed run of stage init-local
------------------------------------------------------------
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/cloudinit/cmd/main.py", line 513, in status_wrap
    ret = functor(name, args)
  File "/usr/lib/python2.7/site-packages/cloudinit/cmd/main.py", line 254, in main_init
    init.apply_network_config(bring_up=not args.local)
  File "/usr/lib/python2.7/site-packages/cloudinit/stages.py", line 641, in apply_network
    return self.distro.apply_network_config(netcfg, bring_up=bring_up)
  File "/usr/lib/python2.7/site-packages/cloudinit/distros/__init__.py", line 154, in app
    netconfig, bring_up=bring_up)
  File "/usr/lib/python2.7/site-packages/cloudinit/distros/__init__.py", line 143, in _ap
    return self.apply_network(contents, bring_up=bring_up)
  File "/usr/lib/python2.7/site-packages/cloudinit/distros/__init__.py", line 125, in app
    dev_names = self._write_network(settings)
  File "/usr/lib/python2.7/site-packages/cloudinit/distros/arch.py", line 67, in _write_n
    'DNS': str(tuple(info.get('dns-nameservers'))).replace(',', '')
TypeError: 'NoneType' object is not iterable
------------------------------------------------------------

The fix proposed in https://bbs.archlinux.org/viewtopic.php?pid=1662566#p1662566 seems to work for me, namely replacing the line with

'DNS': str(tuple(info.get('dns-nameservers'))).replace(',', '') if info.get('dns-nameservers') != None else None