User accounts.yaml as a backup to user provided credentials

For both model and controller connections, accounts.yaml is required
to have both username and password for connection to be
established. This is not always true, for example, juju
change-user-password actually removes the password from the
accounts.yaml file.

Author: cderici

juju/client/connector.py

@@ -85,6 +85,15 @@ async def connect(self, **kwargs):
             # connected to.
             if self._connection:
                 await self._connection.close()
+
+            account = kwargs.pop('account', {})
+            # Prioritize the username and password that user provided
+            # If not enough, try to patch it with info from accounts.yaml
+            if 'username' not in kwargs and account.get('user'):
+                kwargs.update(username=account.get('user'))
+            if 'password' not in kwargs and account.get('password'):
+                kwargs.update(password=account.get('password'))
+
             self._connection = await Connection.connect(**kwargs)
 
         # Check if we support the target controller
@@ -117,7 +126,7 @@ async def disconnect(self, entity):
             await self._log_connection.close()
             self._log_connection = None
 
-    async def connect_controller(self, controller_name=None, specified_facades=None):
+    async def connect_controller(self, controller_name=None, specified_facades=None, **kwargs):
         """Connect to a controller by name. If the name is empty, it
         connect to the current controller.
         """
@@ -130,16 +139,16 @@ async def connect_controller(self, controller_name=None, specified_facades=None)
 
         proxy = proxy_from_config(controller.get("proxy-config", None))
 
-        await self.connect(
-            endpoint=endpoints,
-            uuid=None,
-            username=accounts.get("user"),
-            password=accounts.get("password"),
-            cacert=controller.get("ca-cert"),
-            bakery_client=self.bakery_client_for_controller(controller_name),
-            specified_facades=specified_facades,
-            proxy=proxy,
-        )
+        kwargs.update(endpoint=endpoints,
+                      uuid=None,
+                      account=accounts,
+                      cacert=controller.get('ca-cert'),
+                      bakery_client=self.bakery_client_for_controller(controller_name),
+                      specified_facades=specified_facades,
+                      proxy=proxy,
+                      )
+        await self.connect(**kwargs)
+        self.controller_name = controller_name
         self.controller_uuid = controller["uuid"]
 
     async def connect_model(self, _model_name=None, **kwargs):
@@ -184,15 +193,12 @@ async def connect_model(self, _model_name=None, **kwargs):
 
         # TODO remove the need for base.CleanModel to subclass
         # JujuData.
-        kwargs.update(
-            endpoint=endpoints,
-            uuid=model_uuid,
-            username=account.get("user"),
-            password=account.get("password"),
-            cacert=controller.get("ca-cert"),
-            bakery_client=self.bakery_client_for_controller(controller_name),
-            proxy=proxy,
-        )
+        kwargs.update(endpoint=endpoints,
+                      uuid=model_uuid,
+                      account=account,
+                      cacert=controller.get('ca-cert'),
+                      bakery_client=self.bakery_client_for_controller(controller_name),
+                      proxy=proxy)
         await self.connect(**kwargs)
         # TODO this might be a good spot to trigger refreshing the
         # local cache (the connection to the model might help)