Rack controller failing to register with region controller

[Blake Rouse]

Using latest "master" on a fresh installation of MAAS from "make package" the rackd is failing to register with the region controller:

2019-10-16 18:04:37 RegionServer,299,::ffff:192.168.122.2: [info] RegionServer connection lost (HOST:IPv6Address(TCP, '::ffff:192.168.122.2', 5251) PEER:IPv6Address(TCP, '::ffff:192.168.122.2', 44334))
2019-10-16 18:04:37 metadataserver.builtin_scripts.hooks: [error] maas: Unable to discover NIC IP addresses due to missing passed output from 40-maas-01-network-interfaces
2019-10-16 18:04:37 maasserver.rpc.regionservice: [critical] Failed to register rack controller 'None' with the master. Connection will be dropped.
 Traceback (most recent call last):
   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/twisted/internet/defer.py", line 1442, in gotResult
     _inlineCallbacks(r, g, deferred)
   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)
 --- <exception caught here> ---
   File "/usr/lib/python3/dist-packages/maasserver/rpc/regionservice.py", line 743, in _register
     version=version,
   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 884, in callInContext
     return func(*args, **kwargs)
   File "/usr/lib/python3/dist-packages/provisioningserver/utils/twisted.py", line 216, in wrapper
     result = func(*args, **kwargs)
   File "/usr/lib/python3/dist-packages/maasserver/utils/orm.py", line 691, in call_with_connection
     return func(*args, **kwargs)
   File "/usr/lib/python3/dist-packages/maasserver/utils/__init__.py", line 189, in call_with_lock
     return func(*args, **kwargs)
   File "/usr/lib/python3/dist-packages/maasserver/utils/orm.py", line 736, in call_within_transaction
     return func_outside_txn(*args, **kwargs)
   File "/usr/lib/python3/dist-packages/maasserver/utils/orm.py", line 539, 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/rpc/rackcontrollers.py", line 168, in register
     rackcontroller.update_interfaces(interfaces, create_fabrics=create_fabrics)
   File "/usr/lib/python3/dist-packages/provisioningserver/utils/twisted.py", line 216, in wrapper
     result = func(*args, **kwargs)
   File "/usr/lib/python3/dist-packages/maasserver/utils/orm.py", line 691, in call_with_connection
     return func(*args, **kwargs)
   File "/usr/lib/python3/dist-packages/maasserver/utils/__init__.py", line 189, in call_with_lock
     return func(*args, **kwargs)
   File "/usr/lib/python3/dist-packages/maasserver/utils/orm.py", line 720, in call_within_transaction
     return func_within_txn(*args, **kwargs)
   File "/usr/lib/python3.6/contextlib.py", line 52, in inner
     return func(*args, **kwds)
   File "/usr/lib/python3/dist-packages/maasserver/models/node.py", line 6686, in update_interfaces
     interfaces_details = parse_interfaces_details(self)
   File "/usr/lib/python3/dist-packages/metadataserver/builtin_scripts/hooks.py", line 175, in parse_interfaces_details
     return _parse_interfaces(node, details)
   File "/usr/lib/python3/dist-packages/metadataserver/builtin_scripts/hooks.py", line 127, in _parse_interfaces
     assert isinstance(script_result.output, bytes)
 builtins.AttributeError: 'NoneType' object has no attribute 'output'

2019-10-16 18:04:37 maasserver.rpc.regionservice: [info] Rack controller 'None' disconnected.

[Lee Trager (ltrager)]

This was introduced in acbaf41a799eb84b227eefd7ce499e0842dd8efd. Reverting it fixed things for me.