Comment 1 for bug 1816432

Weird thing noticed, which seems unrelated, is this:

2019-02-18 14:33:03 maasserver.rack_controller: [critical] Failed configuring DHCP on rack controller 'id:249'.
 Traceback (most recent call last):
   File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 1442, in gotResult
     _inlineCallbacks(r, g, deferred)
   File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 1432, in _inlineCallbacks
     deferred.errback()
   File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 500, in errback
     self._startRunCallbacks(fail)
   File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 567, in _startRunCallbacks
     self._runCallbacks()
 --- <exception caught here> ---
   File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 653, in _runCallbacks
     current.result = callback(current.result, *args, **kw)
   File "/usr/lib/python3/dist-packages/maasserver/rack_controller.py", line 256, in <lambda>
     d.addErrback(lambda f: f.trap(NoConnectionsAvailable))
   File "/usr/lib/python3/dist-packages/twisted/python/failure.py", line 359, in trap
     self.raiseException()
   File "/usr/lib/python3/dist-packages/twisted/python/failure.py", line 385, in raiseException
     raise self.value.with_traceback(self.tb)
   File "/usr/lib/python3/dist-packages/twisted/internet/defer.py", line 1384, in _inlineCallbacks
     result = result.throwExceptionIntoGenerator(g)
   File "/usr/lib/python3/dist-packages/twisted/python/failure.py", line 408, in throwExceptionIntoGenerator
     return g.throw(self.type, self.value, self.tb)
   File "/usr/lib/python3/dist-packages/maasserver/dhcp.py", line 751, in configure_dhcp
     config = yield deferToDatabase(get_dhcp_configuration, rack_controller)
   File "/usr/lib/python3/dist-packages/twisted/python/threadpool.py", line 250, in inContext
     result = inContext.theWork()
   File "/usr/lib/python3/dist-packages/twisted/python/threadpool.py", line 266, in <lambda>
     inContext.theWork = lambda: context.call(ctx, func, *args, **kw)
   File "/usr/lib/python3/dist-packages/twisted/python/context.py", line 122, in callWithContext
     return self.currentContext().callWithContext(ctx, func, *args, **kw)
   File "/usr/lib/python3/dist-packages/twisted/python/context.py", line 85, in callWithContext
     return func(*args,**kw)
   File "/usr/lib/python3/dist-packages/provisioningserver/utils/twisted.py", line 885, in callInContext
     return func(*args, **kwargs)
   File "/usr/lib/python3/dist-packages/provisioningserver/utils/twisted.py", line 234, in wrapper
     result = func(*args, **kwargs)
   File "/usr/lib/python3/dist-packages/maasserver/utils/orm.py", line 756, in call_within_transaction
     return func_outside_txn(*args, **kwargs)
   File "/usr/lib/python3/dist-packages/maasserver/utils/orm.py", line 563, in retrier
     return func(*args, **kwargs)
   File "/usr/lib/python3.6/contextlib.py", line 52, in inner
     return func(*args, **kwds)
   File "/usr/lib/python3/dist-packages/maasserver/dhcp.py", line 684, in get_dhcp_configuration
     dhcp_snippets=dhcp_snippets, use_rack_proxy=use_rack_proxy)
   File "/usr/lib/python3/dist-packages/maasserver/dhcp.py", line 578, in get_dhcp_configure_for
     vlan, rack_controller)
   File "/usr/lib/python3/dist-packages/maasserver/dhcp.py", line 454, in make_failover_peer_config
     peer_address = get_ip_address_for_rack_controller(peer_rack, vlan)
   File "/usr/lib/python3/dist-packages/maasserver/dhcp.py", line 247, in get_ip_address_for_rack_controller
     return get_ip_address_for_interface(interface, vlan)
   File "/usr/lib/python3/dist-packages/maasserver/dhcp.py", line 228, in get_ip_address_for_interface
     for ip_address in interface.ip_addresses.all():