title: Wagtail wagtailcore issue "NOT NULL constraint failed: wagtailcore_page.translation_key"
body: <p>I am getting the error message on any call of Page model save method.</p>
  <pre><code>django.db.utils.IntegrityError: NOT NULL constraint failed: wagtailcore_page.translation_key
  </code></pre>
  <p>One of the Page Models looks like this</p>
  <pre><code>@register_query_field('home_page')
  class HomePage(BasePageAbstract):
      
  body = StreamField(
          BasePageAbstract.stream_blocks + [
          ],
          null=True,
          blank=True
      )
  
      content_panels = BasePageAbstract.content_panels + [
          StreamFieldPanel('body', classname=&quot;full&quot;)
          ]
      parent_page_types = None
  
      graphql_fields = [
          GraphQLString(&quot;body&quot;)
      ]
  </code></pre>
  <p>with abstract class</p>
  <pre><code>class BasePageAbstract(Page):
  
  title_image = models.ForeignKey(
      'wagtailimages.Image',
      null=True,
      blank=False,
      on_delete=models.SET_NULL,
      related_name='+'
      )
  
  sub_title_text = models.CharField(max_length=500, blank=True, null=True)
  
  stream_blocks = [
      ('collection', CollectionBlock()),
      (&quot;rich_text&quot;, blocks.RichtextBlock()),
  ]
  
  content_panels = [MultiFieldPanel([
      ImageChooserPanel('title_image'),
      FieldPanel('sub_title_text', widget=forms.Textarea(attrs={'rows':5})),
  ])] + Page.content_panels
  
  
  class Meta:
      abstract = True
  </code></pre>
  <p>Django = &quot;==2.2.5&quot;</p>
  <p>wagtail = &quot;==2.6.1&quot;</p>
  <p>In my database the table wagtailcore_page and the field translation_key are created. So I think it could be a problem with the uuid creation.</p>
  <p>I tried deleting and re-migrating the Page models - no success.
  I also tried updating wagtail - no success.</p>
  <p>I do not really have a clue on how to get closer to a solution of this problem.</p>
  <p>I'd appreciate any help. I will supply more info if helpful.</p>
  <p>Best regards!</p>