Use the nicer way to check if using old client

instead of checking individual facade versions

Author: cderici

juju/machine.py

@@ -22,7 +22,7 @@ async def destroy(self, force=False):
         Blocks until the machine is actually removed.
 
         """
-        if client.MachineManagerFacade.best_facade_version(self.connection) <= 6:
+        if self.connection.is_using_old_client:
             # Then we'll use the DestroyMachines from client.ClientFacade
             facade = client.ClientFacade.from_connection(self.connection)
             await facade.DestroyMachines(force=force, machine_names=[self.id])

juju/model.py

@@ -2012,7 +2012,7 @@ async def get_constraints(self):
         """
         constraints = {}
         facade_cls = client.ModelConfigFacade
-        if facade_cls.best_facade_version(self.connection()) <= 2:
+        if self.connection().is_using_old_client:
             facade_cls = client.ClientFacade
 
         facade = facade_cls.from_connection(self.connection())
@@ -2134,7 +2134,7 @@ async def set_constraints(self, constraints):
         :param dict config: Mapping of model constraints
         """
         facade_cls = client.ModelConfigFacade
-        if facade_cls.best_facade_version(self.connection()) <= 2:
+        if self.connection().is_using_old_client:
             facade_cls = client.ClientFacade
         facade = facade_cls.from_connection(self.connection())
 

juju/provisioner.py

@@ -307,8 +307,7 @@ async def install_agent(self, connection, nonce, machine_id):
         disable_package_commands = False
 
         facade_cls = client.MachineManagerFacade
-
-        if facade_cls.best_facade_version(connection) <= 6:
+        if connection.is_using_old_client:
             facade_cls = client.ClientFacade
 
         facade = facade_cls.from_connection(connection)