title: Django RuntimeWarning: DateTimeField received a naive datetime
body: <p>I'm dockerizing my Django application. Since I changed my database from SQLite to Postgres the migration fails and I get this error:</p>
  
  <pre><code>RuntimeWarning: DateTimeField Posts.created_at received a naive datetime (2020-01-19 14:26:30.893128) while time zone support is active.
    warnings.warn("DateTimeField %s received a naive datetime (%s)"
  Traceback (most recent call last):
    File "/usr/local/lib/python3.8/site-packages/django/db/backends/utils.py", line 86, in _execute
      return self.cursor.execute(sql, params)
  psycopg2.errors.CannotCoerce: cannot cast type time without time zone to timestamp with time zone
  LINE 1: ..." TYPE timestamp with time zone USING "created_at"::timestam...
  </code></pre>
  
  <p>I have searched the other issues and tried this fix <a href="https://stackoverflow.com/a/20106079/7400518">https://stackoverflow.com/a/20106079/7400518</a> <br>
  I was using <code>datetime.now()</code> then I changed it to <code>timezone.now()</code> but I'm still getting the same error.
  This is the related lines from <code>models.py</code></p>
  
  <pre><code>from django.utils import timezone
  
  class Posts(models.Model):
      created_at = models.DateTimeField(default=timezone.now(), blank=True)
  
  </code></pre>