title: What is the benefits of RAC schedule vs responding to subscriber immediately?
body: <p>Could you clarify why RACErrorSignal is do sendError through subscriptionScheduler as shown below but not immediately calling sendError to subscriber?</p>
  
  <pre><code>- (RACDisposable *)subscribe:(id&lt;RACSubscriber&gt;)subscriber {
  NSCParameterAssert(subscriber != nil);
  
  return [RACScheduler.subscriptionScheduler schedule:^{
      [subscriber sendError:self.error];
  }];
  }
  </code></pre>