title: RuntimeError: Conflicting 'product_product_options' models in application 'catalogue'
body: <p><strong>Version Info:</strong>
  Python 3.4, Django 1.8, Oscar Commerce - VERSION = (1, 2, 1, 'final')</p>
  
  <p>I am trying to customize <code>Products</code> in the catalogue app following the <a href="http://django-oscar.readthedocs.io/en/releases-1.1/howto/how_to_customise_models.html" rel="nofollow">documentation</a>. </p>
  
  <p>Having forked the <code>catalogue</code> app, I have defined  <code>models.py</code> as follows:</p>
  
  <pre><code>from django.db import models
  from oscar.apps.catalogue.abstract_models import AbstractProduct
  
  class Product(AbstractProduct):
      is_active = models.BooleanField(default=False)
  
  from oscar.apps.catalogue.models import *
  </code></pre>
  
  <p>I have already included the modified catalogue, in the <code>INSTALLED_APPS</code> in  <code>settings.py</code> as a list,  as suggested for a similar problem <a href="https://groups.google.com/forum/#!topic/django-oscar/nuTP_LhS3p4" rel="nofollow">here</a>.</p>
  
  <pre><code>INSTALLED_APPS = INSTALLED_APPS + get_core_apps(
        ['app.gravytrain.catalogue',])
  </code></pre>
  
  <p>Have copied the migration folder from <code>oscar/apps/catalogue</code> to my custom app.
  However running migration causes the following error:</p>
  
  <pre><code>RuntimeError: Conflicting 'product_product_options' models in
  application 'catalogue': &lt;class
  'gravytrain.catalogue.models.Product_product_options'&gt; and &lt;class
  app.gravytrain.catalogue.models.Product_product_options'&gt;.
  </code></pre>
  
  <p>How do I get over this error ?</p>