title: Angular router: promise returned from navigatebyurl is ignored
body: <p>Using this code:</p>
  
  <p><code>this.router.navigateByUrl('/login');</code></p>
  
  <p>I get the following warning: promise returned from navigatebyurl is ignored. How and when would I want to handle the promise here?</p>
  
  <p>P.S. I'm using this in AuthGuard's <code>canActivate</code>.</p>