python3 -c "from typed_ast import ast27, ast3" doesn't raise an ImportError and yet running mypy keeps telling me:

You must install the typed_ast package before you can run mypy with `--fast-parser`.
You can do this with `python3 -m pip install typed-ast`.

It looks like mypy 0.471 imports typed_ast.ast35 which doesn't exist in typed_ast 1.0.0.