new_contents: # -*- coding: utf-8 -*-
  # Generated by Django 1.10.3 on 2016-12-06 13:02
  from __future__ import unicode_literals
  
  from django.db import migrations
  
  
  def convert_lines_data(apps, schema_editor):
      CartLine = apps.get_model('cart', 'CartLine')
      # Iterate over all cart lines, due to wrong JSONField None handling
      for line in CartLine.objects.all():
          if line.data is None:
              line.data = {}
              line.save(update_fields=['data'])
  
  
  class Migration(migrations.Migration):
  
      dependencies = [
          ('cart', '0002_auto_20161014_1221'),
      ]
  
      operations = [
          migrations.RunPython(convert_lines_data)
      ]
  
subject: Add cart lines data migration