old_contents: # -*- coding: utf-8 -*-
  from __future__ import unicode_literals
  
  from django.db import migrations, models
  
  
  class Migration(migrations.Migration):
  
      dependencies = [
          ('services', '0011_unit_extensions'),
      ]
  
      operations = [
          migrations.AddField(
              model_name='unit',
              name='data_source',
              field=models.CharField(null=True, max_length=20),
          ),
      ]
  
new_contents: # -*- coding: utf-8 -*-
  from __future__ import unicode_literals
  
  from django.db import migrations, models
  
  
  class Migration(migrations.Migration):
  
      dependencies = [
          ('services', '0011_unit_extensions'),
      ]
  
      operations = [
          migrations.AddField(
              model_name='unit',
              name='data_source',
              field=models.CharField(null=True, max_length=20, default='tprek'),
              preserve_default=False
          ),
      ]
  
subject: Add default to data_source migration.