A decorator that ensures context.obj exists. If it doesn't,
    a new dict() is created and stored as obj.

def ensure_obj(f):
    """A decorator that ensures context.obj exists. If it doesn't,
    a new dict() is created and stored as obj.
    """
    @click.pass_context
    def new_func(ctx, *args, **kwargs):
        if ctx.obj is None:
            ctx.obj = {}
        return ctx.invoke(f, *args, **kwargs)
    return update_wrapper(new_func, f)