src/main/java/io/reactivex/Completable.java
@CheckReturnValue
    @NonNull
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Completable takeUntil(CompletableSource other) {
        ObjectHelper.requireNonNull(other, "other is null");

        return RxJavaPlugins.onAssembly(new CompletableTakeUntilCompletable(this, other));
    }
@CheckReturnValue
    @NonNull
    @SchedulerSupport(SchedulerSupport.NONE)
    public final Completable takeUntil(CompletableSource other) {
        ObjectHelper.requireNonNull(other, "other is null");

        return RxJavaPlugins.onAssembly(new CompletableTakeUntilCompletable(this, other));
    }
Terminates the downstream if this or the other {@code Completable}
terminates (wins the termination race) while disposing the connection to the losing source.
<p>
<img width="640" height="468" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Completable.takeuntil.c.png" alt="">
<dl>
<dt><b>Scheduler:</b></dt>
<dd>{@code takeUntil} does not operate by default on a particular {@link Scheduler}.</dd>
<dt><b>Error handling:</b></dt>
<dd>If both this and the other sources signal an error, only one of the errors
is signaled to the downstream and the other error is signaled to the global
error handler via {@link RxJavaPlugins#onError(Throwable)}.</dd>
</dl>
<p>History: 2.1.17 - experimental
@param other the other completable source to observe for the terminal signals
@return the new Completable instance
@since 2.2