new_contents: """
  Removes signatures, so they can be easily recreated during deployment.
  
  This migration is intended to be used between "eras" of signatures. As
  the serialization format of recipes changes, the signatures need to
  also change. This could be handled automatically, but it is easier to
  deploy if we just remove everything in a migration, and allow the
  normal processes to regenerate the signatures.
  """
  
  # -*- coding: utf-8 -*-
  # Generated by Django 1.9.11 on 2017-01-27 00:03
  from __future__ import unicode_literals
  
  from django.db import migrations
  
  
  def remove_signatures(apps, schema_editor):
      Recipe = apps.get_model('recipes', 'Recipe')
      Signature = apps.get_model('recipes', 'Signature')
  
      for recipe in Recipe.objects.exclude(signature=None):
          sig = recipe.signature
          recipe.signature = None
          recipe.save()
          sig.delete()
  
      for sig in Signature.objects.all():
          sig.delete()
  
  
  class Migration(migrations.Migration):
  
      dependencies = [
          ('recipes', '0037_auto_20170113_0627'),
      ]
  
      operations = [
          # This function as both a forward and reverse migration
          migrations.RunPython(remove_signatures, remove_signatures),
      ]
  
subject: Add migration to reset signatures