title: Django (1.7) - data migrations
body: <p>I have created an empty data migration script for populating one of
  app db tables with data from a JSON file, using </p>
  
  <pre><code>python manage.py makemigrations --empty &lt;app name&gt;
  </code></pre>
  
  <p>I want to add data contained in JSON files to the db, which at the moment consists of just one table, using a data migration script (according to Django 1.7 docs this is the recommended approach) using a custom method called <code>populate_db</code> which will use <code>bulk_create</code> to add
  multiple entries to the table, and then do a <code>save()</code> to write the
  changes to the db.  At the moment the custom method is empty
  because I am still working on it, but the script looks like this right
  now</p>
  
  <pre><code># -*- coding: utf-8 -*-
  from __future__ import unicode_literals
  
  from django.db import models, migrations
  
  def populate_db( apps, schema_editor ):
     print ‘Populating db from JSON file...'
  
  class Migration(migrations.Migration):
  
     dependencies = [
         ('&lt;app name&gt;', '0003_auto_20150224_2024'),
     ]
  
     operations = [
                            migrations.RunPython( populate_db ),
     ]
  </code></pre>
  
  <p>How do I test this script to make sure the custom method works
  as expected, before I run it fully?  Can I call this from the interpreter
  and test it with the db API?</p>
  
  <p>At the moment if I do</p>
  
  <pre><code>python manage.py migrate &lt;app name&gt;
  </code></pre>
  
  <p>it reports there are no migrations to apply.</p>