flake8 fixes, PR comments addressed

nailgun/entity_mixins.py

@@ -958,6 +958,7 @@ class EntityUpdateMixin(object):
     :meth:`update_payload`
         Assemble a payload of data that can be encoded and sent to the
         server.
+        Set self.updatable_fields (list of strings) to limit the fields that can be updated.
     :meth:`update_raw`
         Make an HTTP PUT request to the server, including the payload.
     :meth:`update_json`
@@ -979,8 +980,7 @@ def update_payload(self, fields=None):
 
         """
         values = self.get_values()
-        updatable_fields =( self.updatable_fields if hasattr(self, 'updatable_fields') else
-                           values.keys() )
+        updatable_fields = getattr(self, 'updatable_fields', None) or list(values.keys())
         values = {field: value for field, value in values.items() if field in updatable_fields}
         if fields is not None:
             values = {field: values[field] for field in fields}

tests/test_entities.py

@@ -2090,6 +2090,17 @@ def test_media_path(self):
         self.assertNotIn('path_', payload['medium'])
         self.assertIn('path', payload['medium'])
 
+    def test_hostcollection_updatable_fields(self):
+        org1 = entities.Organization(self.cfg, name='org1')
+        org2 = entities.Organization(self.cfg, name='org2')
+        host_collection = entities.HostCollection(self.cfg, name='oldname', organization=org1)
+        host_collection.name = 'newname'
+        host_collection.organization_id = org2
+        payload = host_collection.update_payload()
+        self.assertEquals(payload['name'], 'newname')
+        self.assertNotIn('organization', payload.keys())  # organization NOT changed
+        self.assertNotIn('organization_id', payload.keys())  # organization NOT changed
+
     def test_job_template(self):
         """Create a :class:`nailgun.entities.JobTemplate`."""
         payload = entities.JobTemplate(