get_binding wants a Relation instance

[barryprice]

According to ops/model.py's Model.get_binding(), it will accept either a Relation instance, or a relation name:

    def get_binding(self, binding_key):                                                                                
        """Get a network space binding.                                                                                

        binding_key -- The relation name or instance to obtain bindings for.                                           

        If binding_key is a relation name, the method returns the default binding for that                             
        relation. If a relation instance is provided, the method first looks up a more specific                        
        binding for that specific relation ID, and if none is found falls back to the default                          
        binding for the relation name.                                                                                 
        """                                                                                                            
        return self._bindings.get(binding_key)                                                                         

However, if I pass it a string, set to an appropriate relation name:

Traceback (most recent call last):                                                                                        
  File "/var/lib/juju/agents/unit-wordpress-0/charm/hooks/config-changed", line 276, in <module>                          
    main(Wordpress)                                                                                                       
  File "lib/ops/main.py", line 195, in main                                                                               
    _emit_charm_event(charm, juju_event_name)                                                                             
  File "lib/ops/main.py", line 120, in _emit_charm_event                                                                  
    event_to_emit.emit(*args, **kwargs)                                                                                   
  File "lib/ops/framework.py", line 199, in emit                                                                          
    framework._emit(event)                                                                                                
  File "lib/ops/framework.py", line 633, in _emit                                                                      
    self._reemit(event_path)                                                                                           
  File "lib/ops/framework.py", line 668, in _reemit                                                                       
    custom_handler(event)                                                                                              
  File "/var/lib/juju/agents/unit-wordpress-0/charm/hooks/config-changed", line 50, in on_config_changed               
    self.configure_pod(event)                                                                                             
  File "/var/lib/juju/agents/unit-wordpress-0/charm/hooks/config-changed", line 270, in configure_pod                  
    if self.first_install():                                                                                           
  File "/var/lib/juju/agents/unit-wordpress-0/charm/hooks/config-changed", line 131, in first_install                     
    if not self.is_pod_up("website"):                                                                                  
  File "/var/lib/juju/agents/unit-wordpress-0/charm/hooks/config-changed", line 236, in is_pod_up                         
    ingress = self.get_service_ip(endpoint)                                                                               
  File "/var/lib/juju/agents/unit-wordpress-0/charm/hooks/config-changed", line 232, in get_service_ip                 
    return self.model.get_binding("website").network.ingress_address                                                      
  File "lib/ops/model.py", line 65, in get_binding                                                                     
    return self._bindings.get(relation)                                                                                   
  File "lib/ops/model.py", line 263, in get                                                                               
    raise ModelError('expected Relation instance, got {}'.format(type(relation).__name__))                                
ops.model.ModelError: expected Relation instance, got str                                                                 
ERROR juju.worker.uniter.operation hook "config-changed" failed: exit status 1                                         

[barryprice]

Never mind, stale submodule checkout