Error ClassNotFoundException in Symfony 3 Router

Someone can explain me the following error in Symfony 3.0:

I have created a bundle called blog, for which I defined the path /blog :

blog_homepage:
    path:     /blog
    defaults: { _controller: BlogBundle:Default:index }

When I start working with the entities, I get the following error:

  

ClassNotFoundException in appDevUrlGenerator.php line 14: Attempted to   load class "UrlGenerator" from namespace   "BlogBundle \ Entity \ Symfony \ Component \ Routing \ Generator". Did you   forget to "use" statement for   "Symfony \ Component \ Routing \ Generator \ UrlGenerator"?

After so much testing and testing, the error is corrected if I change the route for another (it should be noted that there is no other route called / blog), for example something like this:

blog_homepage:
    path:     /blogp
    defaults: { _controller: BlogBundle:Default:index }

It is something very absurd, someone can tell me why, and how to correct it.