>>> class TestModel(models.Model):
...    test_field = models.CharField(blank=True, null=True)
...    class Meta:
...        app_label="test"
>>> TestModel.objects.exclude(test_field='').query.__str__()
'SELECT "test_testmodel"."id", "test_testmodel"."test_field" FROM "test_testmodel" WHERE NOT ("test_testmodel"."test_field" =  AND "test_testmodel"."test_field" IS NOT NULL)'
>>> import django
>>> django.VERSION
(2, 2, 4, 'final', 0)
>>> from django.conf import settings
>>> settings.DATABASES
{'default': {'ENGINE': 'django.db.backends.sqlite3', ... }}