I toyed with the idea of using numeric constant for error codes but it seemed to add more requirements (e.g. defining constants) for no big benefit. I use short error messages in simple English that I intend to preserve as-is. That is, "Tag limit exceeded" will not become "The tag limit has been exceeded" in a future version. In that regard, they can be treated as constant and `if ($msg === 'Tag limit exceeded')` should have the same properties as `if ($code === Logger::TAG_LIMIT_EXCEEDED)`