I have updated the stubs now to support Python 2. But I wonder whether we should require contributors to provide Python 2 compatible stubs when they submit new stubs. (Of course existing stubs that support Python 2 should continue to do so.) Making stubs Python 2 compatible requires quite a bit of additional work and it's quite possible that a Python 2 version is not that useful anyway, considering Python 2's end of life date.
Personally I suggest, we accept Python 3-only stubs (and also Python 2-only stubs), even if the library supports both versions. Support for the other Python version can always be added later by an interested party.