title: CompletableFuture.thenAccept equivalent for exceptions
body: <p><code>java.util.concurrent.CompletionStage#exceptionally</code> expects a function that returns a value, but what if I just want a <code>Consumer</code> for a <code>Throwable</code> like <code>java.util.concurrent.CompletionStage#thenAccept</code> for successful executions?</p>
  <p>EDIT: To be clear, I know about <code>whenComplete</code> but that does not &quot;take a <code>Consumer</code> for a <code>Throwable</code> like <code>java.util.concurrent.CompletionStage#thenAccept</code>&quot;.</p>