Use value attribute in tests

tests/test_mock.py

@@ -86,7 +86,7 @@ def test_mock_client():
 
     with pytest.raises(apistar.exceptions.ErrorResponse) as e_info:
         mock.request("DeleteTag", name="Henri", body={"tag": "yyy"})
-    _, error_response, _ = e_info._excinfo
+    error_response = e_info.value
     assert error_response.status_code == 403
     assert error_response.title == "Forbidden"
     assert error_response.content == "You cannot perform this action"