Skip null check for batch delete (#283)

Author: jmphilli

pynamodb/models.py

@@ -1186,7 +1186,7 @@ def _get_keys(self):
         """
         Returns the proper arguments for deleting
         """
-        serialized = self._serialize()
+        serialized = self._serialize(null_check=False)
         hash_key = serialized.get(HASH)
         range_key = serialized.get(RANGE, None)
         hash_keyname = self._get_meta_data().hash_keyname

pynamodb/tests/test_model.py

@@ -837,6 +837,20 @@ def test_delete(self):
             args = req.call_args[0][1]
             deep_eq(args, params, _assert=True)
 
+    def test_delete_doesnt_do_validation_on_null_attributes(self):
+        """
+        Model.delete
+        """
+        with patch(PATCH_METHOD) as req:
+            req.return_value = CAR_MODEL_TABLE_DATA
+            CarModel('foo').delete()
+
+        with patch(PATCH_METHOD) as req:
+            req.return_value = CAR_MODEL_TABLE_DATA
+            with CarModel.batch_write() as batch:
+                car = CarModel('foo')
+                batch.delete(car)
+
     def test_update(self):
         """
         Model.update