Text Editor Sample Dialogs are not showing on windows

Hi,
I'm would like to use Dialogs like in text-editor sample code. But I can't make the sample work.
I'm trying to open the About dialog.
I have python 3.7.2.

I try debugging and it hangs on =>>> result = await dialog.future

async def show_dialog_as_float(dialog):
    " Coroutine. "
    float_ = Float(content=dialog)
    root_container.floats.insert(0, float_)

    app = get_app()

    focused_before = app.layout.current_window
    app.layout.focus(dialog)
    result = await dialog.future
    app.layout.focus(focused_before)

    if float_ in root_container.floats:
        root_container.floats.remove(float_)

    return result

Thank you!

Reproduce the text-editor sample on Windows with Python 3.7.2 and try opening the About dialog. Start at show_dialog_as_float, especially the await dialog.future line; done means the dialog appears and can be dismissed without hanging.