title: Error when targetEntity is in a different bundle
body: <p>I'm getting the following error when I try to do <code>./app/console doctrine:migrate:diff</code>:</p>
  
  <pre><code> [Doctrine\ORM\Mapping\MappingException]                                        
    Class VNN\CoreBundle\Entity\Game is not a valid entity or mapped super class. 
  </code></pre>
  
  <p>Here's the line that's causing it:</p>
  
  <pre><code>/**
   * @ORM\ManyToOne(targetEntity="VNN\CoreBundle\Entity\Game")
  </code></pre>
  
  <p>Here's the relevant part of my class:</p>
  
  <pre><code>&lt;?php
  
  namespace VNN\PressboxBundle\Entity;
  
  use Gedmo\Mapping\Annotation as Gedmo;
  use Doctrine\ORM\Mapping as ORM;
  use Doctrine\ORM\Query\Expr\OrderBy;
  use Symfony\Component\Validator\Constraints as Assert;
  use Symfony\Component\Validator\Mapping\ClassMetadata;
  use Symfony\Component\Validator\Constraints\NotBlank;
  use Symfony\Component\Validator\Constraints\Type;
  use VNN\CoreBundle\Entity\Game;
  
  /**
   * VNN\PressboxBundle\Entity\Event
   *
   * @ORM\Table(name="event")
   * @ORM\Entity
   */
  class Event
  {
      /**
       * @var integer $id
       *
       * @ORM\Column(name="id", type="integer")
       * @ORM\Id
       * @ORM\GeneratedValue(strategy="AUTO")
       */
      private $id;
  
      /**
       * @ORM\ManyToOne(targetEntity="VNN\CoreBundle\Entity\Game")
       * @ORM\JoinColumn(name="core_game_id", referencedColumnName="game_id")
       **/
      private $coreGame;
  </code></pre>
  
  <p>What I understand it's saying is not that it can't <em>find</em> <code>VNN\CoreBundle\Entity\Game</code>, just that <code>Game</code> is not a valid entity. So here's <code>Game.php</code>:</p>
  
  <pre><code>&lt;?php
  
  namespace VNN\CoreBundle\Entity;
  
  use Doctrine\ORM\Mapping as ORM;
  
  /**
   * VNN\CoreBundle\Entity\Game
   *
   * @ORM\Table(name="games")
   * @ORM\Entity
   */
  class Game
  {
      /**
       * @var integer $id
       *
       * @ORM\Column(name="game_id", type="integer")
       * @ORM\Id
       * @ORM\GeneratedValue(strategy="AUTO")
       */
      private $id;
  
      /**
       * @var integer $homeSchoolId
       *
       * @ORM\Column(name="home_school_id", type="integer")
       */
      private $homeSchoolId;
  
      /**
       * @var integer $awaySchoolId
       *
       * @ORM\Column(name="away_school_id", type="integer")
       */
      private $awaySchoolId;
  
      /**
       * @ORM\ManyToOne(targetEntity="School")
       * @ORM\JoinColumn(name="home_school_id", referencedColumnName="school_id")
       **/
      private $homeSchool;
  
      /**
       * @ORM\ManyToOne(targetEntity="School")
       * @ORM\JoinColumn(name="away_school_id", referencedColumnName="school_id")
       **/
      private $awaySchool;
  
      /**
       * @ORM\ManyToOne(targetEntity="Sport")
       * @ORM\JoinColumn(name="sport_id", referencedColumnName="sport_id")
       **/
      private $sport;
  
      /**
       * @var integer $datetime
       *
       * @ORM\Column(name="game_datetime")
       */
      private $datetime;
  
      /**
       * @var integer $homeScore
       *
       * @ORM\Column(name="home_score", type="integer")
       */
      private $homeScore;
  
      /**
       * @var integer $awayScore
       *
       * @ORM\Column(name="away_score", type="integer")
       */
      private $awayScore;
  
      public function getId()
      {
          return $this-&gt;id;
      }
  
      public function getHomeSchool()
      {
          if ($this-&gt;homeSchoolId &gt; 0) {
              return $this-&gt;homeSchool;
          } else {
              return FALSE;
          }
      }
  
      public function getAwaySchool()
      {
          if ($this-&gt;awaySchoolId &gt; 0) {
              return $this-&gt;awaySchool;
          } else {
              return FALSE;
          }
      }
  
      public function recordIsValid()
      {
          if (!($this-&gt;homeSchoolId &gt; 0)) {
              return FALSE;
          }
  
          if (!($this-&gt;awaySchoolId &gt; 0)) {
              return FALSE;
          }
  
          return TRUE;
      }
  
      public function getSport()
      {
          return $this-&gt;sport;
      }
  
      public function getHumanDatetime()
      {
          $date = new \DateTime($this-&gt;datetime);
          return $date-&gt;format('F d, Y g:ia');
      }
  
      public function getDatetime()
      {
          $date = new \DateTime($this-&gt;datetime);
          return $date-&gt;format('m/d/Y g:i:s a');
      }
  
      public function getOpposingSchoolWithRespectToSchoolName($schoolName)
      {
          if ($schoolName == $this-&gt;getHomeSchool()-&gt;getName()) {
              return $this-&gt;getAwaySchool();
          } else {
              return $this-&gt;getHomeSchool();
          }
      }
  
      public function getHomeScore()
      {
          return $this-&gt;homeScore;
      }
  
      public function getAwayScore()
      {
          return $this-&gt;awayScore;
      }
  }
  </code></pre>
  
  <p>Why would it not like <code>Game</code>?</p>
  
  <p>Update: I had this same exact problem again when I tried to do the same thing with another cross-bundle entity. I found <a href="https://stackoverflow.com/questions/7688602/how-can-i-use-a-different-namespace-class-in-doctrine2-targetentity-mapping">this post</a>, but the add-a-leading-slash fix didn't do it for me like it evidently did for the OP there.</p>