public static class ImmediateSupplier.ImmediateValueNotAvailableException
Indicates that an attempt was made to forcibly get a requested immediate value
where blocking is required. See ImmediateSupplier.getImmediately(), which if
it returns an absent result, that absent will throw this.
This is useful for passing between contexts that support immediate evaluation,
through contexts that do not, to outer contexts which do, as the outer context
will be able to use this exception to return a Maybe.absent() rather than throwing.