uuid(3|5) generation does not accept names which are not utf-8 decodable

From the documentation: 
```
uuid.uuid3(namespace, name)
Generate a UUID based on the MD5 hash of a namespace identifier (which is a UUID) and a name (which is a string).
```

As far as I can tell from RFC4122, name being a string is not a requirement and therefore there are UUIDs which we cannot generate. Is this a bug or am I missing something from the RFC?