title: Revisions not creating in TestCase ( Django, django-reversion, tests)
body: <p>Trying to cover with tests <code>django-reversion</code> functionality for my model, but versions are not created in test db, in manual creation from admin interface everything works fine.</p>
  <p>Model:</p>
  <pre><code>@reversion.register()
  class RuleSet(ModeratedBase, AdminUrlMixin):
      &quot;&quot;&quot;Ruleset of a given type of contest related to the contest&quot;&quot;&quot;
  
      name = models.CharField(
          max_length=64,
          help_text=&quot;Short name of the ruleset.&quot;,
          unique=True
      )
      rules = models.JSONField(
          default=dict,
          help_text=&quot;Base rules dict for Ruleset&quot;,
          blank=True,
          null=True,
      )
      default_for = models.ManyToManyField(
          &quot;ci_contest.ContestType&quot;,
          help_text=&quot;Field specifies content types ruleset is default for&quot;,
          related_name=&quot;default_ruleset&quot;,
          null=True,
          blank=True,
      )
  
      def __str__(self):
          return self.name
  
      def get_versions(self):
          return Version.objects.get_for_object(self)
  </code></pre>
  <p>Test:</p>
  <pre><code> class RulesetTestCase(TestCase):
      fixtures = [&quot;core-defaults&quot;, &quot;gamer-defaults&quot;, &quot;ledger-defaults&quot;, &quot;contest-defaults&quot;]
  
      def setUp(self):
          call_command(&quot;createinitialrevisions&quot;)
          self.ruleset = RuleSetFactory()
  
      def test_ruleset_get_versions(self):
          self.assertFalse(self.ruleset.get_versions().exists())
          self.ruleset.rules = str(fake.pydict())
          self.ruleset.save()
          print(self.ruleset.get_versions())
          self.assertTrue(self.ruleset.get_versions().exists())
  </code></pre>
  <p>Print Output:</p>
  <pre><code>&lt;VersionQuerySet []&gt;
  </code></pre>