Fix _resolve_charm errors

That are accidentally introduced in #825.

* _resolve_charm's force parameter is made optional
* fixed the _resolve_charm calls in bundle.py to have less number of
variables to unpack onto

Author: cderici

juju/bundle.py

@@ -366,10 +366,8 @@ async def _resolve_charms(self):
                                             architecture=architecture,
                                             risk=risk,
                                             track=track)
-                if not self.model.connection().is_using_old_client and series:
-                    origin.base = client.Base(
-                        channel=utils.get_series_version(series), name='ubuntu')
-                charm_url, charm_origin, _ = await self.model._resolve_charm(charm_url, origin)
+
+                charm_url, charm_origin = await self.model._resolve_charm(charm_url, origin)
                 spec['charm'] = str(charm_url)
             else:
                 charm_origin = client.CharmOrigin(source=Source.CHARM_HUB.value,
@@ -719,11 +717,7 @@ async def run(self, context):
                                         architecture=arch,
                                         risk=ch.risk,
                                         track=ch.track)
-            if not context.model.connection().is_using_old_client and self.series:
-                origin.base = client.Base(
-                    channel=utils.get_series_version(self.series),
-                    name='ubuntu')
-            identifier, origin, _ = await context.model._resolve_charm(url, origin)
+            identifier, origin = await context.model._resolve_charm(url, origin)
 
         if identifier is None:
             raise JujuError('unknown charm {}'.format(self.charm))

juju/model.py

@@ -1790,8 +1790,7 @@ async def _add_charm(self, charm_url, origin):
         client_facade = client.ClientFacade.from_connection(self.connection())
         return await client_facade.AddCharm(channel=str(origin.risk), url=charm_url, force=False)
 
-
-    async def _resolve_charm(self, url, origin, force):
+    async def _resolve_charm(self, url, origin, force=False):
         """Calls Charms.ResolveCharms to resolve all the fields of the
         charm_origin and also the url and the supported_series
 
@@ -1844,7 +1843,7 @@ async def _resolve_charm(self, url, origin, force):
             else:
                 raise JujuError("Series {} not supported for {}. Only {}".format(origin.series, result.url, supported_series))
 
-        return charm_url, result.charm_origin
+        return result.url, result.charm_origin
 
     async def _resolve_architecture(self, url):
         if url.architecture: