src/main/java/io/reactivex/Completable.java
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Completable repeatWhen(Function<? super Flowable<Object>, ? extends Publisher<?>> handler) {
        return fromPublisher(toFlowable().repeatWhen(handler));
    }
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Completable repeatWhen(Function<? super Flowable<Object>, ? extends Publisher<?>> handler) {
        return fromPublisher(toFlowable().repeatWhen(handler));
    }
Returns a Completable instance that repeats when the Publisher returned by the handler
emits an item or completes when this Publisher emits a completed event.
<p>
<img width="640" height="586" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Completable.repeatWhen.png" alt="">
<dl>
<dt><b>Scheduler:</b></dt>
<dd>{@code repeatWhen} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>
@param handler the function that transforms the stream of values indicating the completion of
this Completable and returns a Publisher that emits items for repeating or completes to indicate the
repetition should stop
@return the new Completable instance
@throws NullPointerException if stop is null