src/main/java/io/reactivex/Single.java
@CheckReturnValue
    @NonNull
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Single<T> takeUntil(final CompletableSource other) {
        ObjectHelper.requireNonNull(other, "other is null");
        return takeUntil(new CompletableToFlowable<T>(other));
    }
@CheckReturnValue
    @NonNull
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Single<T> takeUntil(final CompletableSource other) {
        ObjectHelper.requireNonNull(other, "other is null");
        return takeUntil(new CompletableToFlowable<T>(other));
    }
Returns a Single that emits the item emitted by the source Single until a Completable terminates. Upon
termination of {@code other}, this will emit a {@link CancellationException} rather than go to
{@link SingleObserver#onSuccess(Object)}.
<p>
<img width="640" height="380" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/takeUntil.png" alt="">
<dl>
<dt><b>Scheduler:</b></dt>
<dd>{@code takeUntil} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>

@param other
the Completable whose termination will cause {@code takeUntil} to emit the item from the source
Single
@return a Single that emits the item emitted by the source Single until such time as {@code other} terminates.
@see <a href="http://reactivex.io/documentation/operators/takeuntil.html">ReactiveX operators documentation: TakeUntil</a>