src/main/java/io/reactivex/Completable.java
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public static Completable never() {
        return RxJavaPlugins.onAssembly(CompletableNever.INSTANCE);
    }
@CheckReturnValue
    @SchedulerSupport(SchedulerSupport.NONE)
    public static Completable never() {
        return RxJavaPlugins.onAssembly(CompletableNever.INSTANCE);
    }
Returns a Completable that never calls onError or onComplete.
<p>
<img width="640" height="512" src="https://raw.github.com/wiki/ReactiveX/RxJava/images/rx-operators/Completable.never.png" alt="">
<dl>
<dt><b>Scheduler:</b></dt>
<dd>{@code never} does not operate by default on a particular {@link Scheduler}.</dd>
</dl>
@return the singleton instance that never calls onError or onComplete