title: Django: "Invalid default value" during "migrate" command
body: <p>There is a simple model</p>
  
  <pre><code>class Baz(models.Model):
    FOO = ('foo', 'Foo')
    BAR = ('bar', 'Bar')
    FOO_BAR = (FOO, BAR)
  
    foo_bar = models.CharField(max_length=5, default=FOO, choices=FOO_BAR)
  </code></pre>
  
  <p>After making migrations via <code>python manage.py makemigrations</code>, when trying to migrate, getting error:</p>
  
  <pre><code>django.db.utils.OperationalError: (1067, "Invalid default value for 'foo_bar'")
  </code></pre>
  
  <p>Tried to put <code>('foo', 'Foo')</code> explicitly with no result. Tried to use <code>FOO_BAR[0]</code> - same error.</p>
  
  <p>Any ideas?</p>