Fix dynamo item not found.

moto/dynamodb2/models.py

@@ -381,6 +381,7 @@ class DynamoDBBackend(BaseBackend):
     def get_item(self, table_name, keys):
         table = self.get_table(table_name)
         if not table:
+            raise ValueError()
             return None
         hash_key, range_key = self.get_keys_value(table, keys)
         return table.get_item(hash_key, range_key)

moto/dynamodb2/responses.py

@@ -196,8 +196,8 @@ class DynamoHandler(BaseResponse):
             return dynamo_json_dump(item_dict)
         else:
             # Item not found
-            er = 'com.amazonaws.dynamodb.v20111205#ResourceNotFoundException'
-            return self.error(er, status=404)
+            er = '{}'
+            return self.error(er, status=200)
 
     def batch_get_item(self):
         table_batches = self.body['RequestItems']