style fix

Author: wjakob

tests/test_python_types.py

@@ -513,6 +513,7 @@ def test_builtins_cast_return_none():
     assert m.return_none_int() is None
     assert m.return_none_float() is None
 
+
 def test_capsule_with_destructor(capture):
     import pybind11_tests as m
     with capture: