vlans are not correctly dehydrated

[lutostag]

In [2]: from maas.client import connect

In [3]: maas = connect('http://10.48.0.230:5240/MAAS', apikey='***')                        

In [4]: other = maas.subnets.list()[0] 

In [5]: other.vlan = other.vlan        

In [6]: other.save()                   
---------------------------------------------------------------------------    
AssertionError                            Traceback (most recent call last)    
<ipython-input-6-01f21911bae3> in <module>()                                   
----> 1 other.save()                   

~/.virtualenvs/mmm/lib/python3.6/site-packages/maas/client/utils/async.py in wrapper(*args, **kwargs)                                                          
     47         if not eventloop.is_running():                                 
     48             while isawaitable(result):                                 
---> 49                 result = eventloop.run_until_complete(result)          
     50         return result          
     51                                

/usr/lib/python3.6/asyncio/base_events.py in run_until_complete(self, future)  
    465             raise RuntimeError('Event loop stopped before Future completed.')                                                                          
    466                                
--> 467         return future.result() 
    468                                
    469     def stop(self):            

~/.virtualenvs/mmm/lib/python3.6/site-packages/maas/client/viscera/__init__.py in save(self)                                                                   
    480                     for key in self._handler.params                    
    481                 })             
--> 482                 self._data = await self._handler.update(**update_data) 
    483         else:                  
    484             raise AttributeError(                                      

~/.virtualenvs/mmm/lib/python3.6/site-packages/maas/client/bones/__init__.py in __call__(self, **data)                                                         
    300             if key.startswith('_'):                                    
    301                 data[key[1:]] = data.pop(key)                          
--> 302         response = await self.bind(**params).call(**data)              
    303         return response.data   
    304                                

~/.virtualenvs/mmm/lib/python3.6/site-packages/maas/client/bones/__init__.py in call(self, **data)                                                             
    388         :param data: Data to pass in the *body* of the request.        
    389         """                    
--> 390         uri, body, headers = self.prepare(data)                        
    391         return self.dispatch(uri, body, headers)                       
    392                                

~/.virtualenvs/mmm/lib/python3.6/site-packages/maas/client/bones/__init__.py in prepare(self, data)                                                            
    418         # Bundle things up ready to throw over the wire.               
    419         uri, body, headers = utils.prepare_payload(                    
--> 420             self.action.op, self.action.method, self.uri, data)        
    421                                
    422         # Headers are returned as a list, but they must be a dict for  

~/.virtualenvs/mmm/lib/python3.6/site-packages/maas/client/utils/__init__.py in prepare_payload(op, method, uri, data)                                         
    109         # Even if data is empty, construct a multipart request body. Piston                                                                            
    110         # (server-side) sets `request.data` to `None` if there's no payload.                                                                           
--> 111         message = build_multipart_message(data)                        
    112         headers, body = encode_multipart_message(message)              
    113                                

~/.virtualenvs/mmm/lib/python3.6/site-packages/maas/client/utils/multipart.py in build_multipart_message(data)                                                 
    122     message = MIMEMultipart("form-data")                               
    123     for name, content in data: 
--> 124         for payload in make_payloads(name, content):                   
    125             message.attach(payload)                                    
    126     return message             

~/.virtualenvs/mmm/lib/python3.6/site-packages/maas/client/utils/multipart.py in make_payloads(name, content)                                                  
    112     elif isinstance(content, Iterable):                                
    113         for part in content:   
--> 114             for payload in make_payloads(name, part):                  
    115                 yield payload  
    116     else:                      

~/.virtualenvs/mmm/lib/python3.6/site-packages/maas/client/utils/multipart.py in make_payloads(name, content)                                                  
    116     else:                      
    117         raise AssertionError(  
--> 118             "%r is unrecognised: %r" % (name, content))                
    119                                
    120                                

AssertionError: 'vlan' is unrecognised: <Fabric id=0 (unloaded)>               

In [7]: 

This is just a small repro. I am obviously trying to set it to a different vlan, this is just the most concise repro I could get.