title: /django.db.utils.IntegrityError: NOT NULL constraint failed/ after python manage.py migrate app zero
body: <p>I had some mess with migrations in production and localy. Finally the situation was that in production there were only initial migration and localy there were 8 migrations or something. So I decided to use </p>
  
  <pre><code>python manage.py migrate app zero 
  </code></pre>
  
  <p>both in production and localy(django 1.8.7). In prodcution it worked but locally it raised error which didn't appear before after <code>makemigrations</code> or <code>migrate</code> command. </p>
  
  <pre><code>django.db.utils.IntegrityError: NOT NULL constraint failed: app_userprofile__new.phone_number
  </code></pre>
  
  <p>after few attempts to try different things, the error began to appear after migrate commands too.</p>
  
  <p>The model itself :</p>
  
  <pre><code>class UserProfile(models.Model):
      user = models.OneToOneField(User)
      phone_number = models.IntegerField(null=True, blank=True, default=None)
  </code></pre>