Function poll_until 

pub async fn poll_until<T, F, Fut>(
    what: impl Display + Send,
    poll: F,
) -> Result<T>
where
    F: FnMut() -> Fut,
    Fut: Future<Output = Result<Option<T>>>,

Calls poll every POLL_INTERVAL until it returns a value.

Returns an error describing what was awaited if the condition is not met within WAIT_TIMEOUT, or the first error returned by poll. This is poll_until_with with the default PollOpts, see there for when poll is called.

what is held across awaits, so it must be Send for the returned future to be Send. This rules out format_args!, use format! instead.