title: FieldError: Cannot resolve keyword 'XXXX' into field
body: <p>This is a very strange error. I only receive it on my heroku server. </p>
  
  <p>Here is how my model is: </p>
  
  <pre><code># Abstract Model
  
  class CommonInfo(models.Model):
      active = models.BooleanField('Enabled?', default=False)
      date_created = models.DateTimeField(auto_now_add=True)
      date_updated = models.DateTimeField(auto_now=True)
  
      class Meta:
          abstract = True
  
  
  class Country(CommonInfo):
      name = models.CharField('Country Name', db_index=True, max_length=200, help_text='e.g. France')
      official_name = models.CharField('Official Name', max_length=400, blank=True, help_text='e.g. French Republic')
      population = models.IntegerField('Population', help_text='Population must be entered as numbers with no commas or separators, e.g. 39456123', null=True, blank=True)
      alpha2 = models.CharField('ISO ALPHA-2 Code', max_length=2, blank=True)
  
  
  class News(CommonInfo):
      title = models.CharField('Title', max_length=250)
      slug = models.CharField('slug', max_length=255, unique=True)
      body = models.TextField('Body', null=True, blank=True)
      excerpt = models.TextField('Excerpt', null=True, blank=True)
      author = models.ForeignKey(Author)
      country = models.ManyToManyField(Country, null=True, blank=True)
  
      def __unicode__(self):
              return self.title
  </code></pre>
  
  <p>When I try to access News items from Admin site on my production server, I get this error (everything works fine on my dev server):</p>
  
  <pre><code>FieldError: Cannot resolve keyword 'news' into field. Choices are: active, alpha2, date_created, date_updated, id, name, official_name, population
     File "/app/.heroku/python/lib/python2.7/site-packages/django/db/models/query.py", line 687, in _filter_or_exclude
       clone.query.add_q(Q(*args, **kwargs)) 
     File "/app/.heroku/python/lib/python2.7/site-packages/django/db/models/sql/query.py", line 1271, in add_q
       can_reuse=used_aliases, force_having=force_having)
     File "/app/.heroku/python/lib/python2.7/site-packages/django/db/models/sql/query.py", line 1139, in add_filter
       process_extras=process_extras)
     File "/app/.heroku/python/lib/python2.7/site-packages/django/db/models/sql/query.py", line 1337, in setup_joins
       "Choices are: %s" % (name, ", ".join(names)))
  </code></pre>
  
  <p>I run the same django (1.5.4) and python (2.7.2) versions on my production and development environments. </p>
  
  <p>My production server is Heroku</p>
  
  <p>Any ideas what could triggers the error?</p>
  
  <p><strong>UPDATE</strong>:</p>
  
  <p>admin.py config is as follow:</p>
  
  <pre><code>from django.contrib import admin
  from APP.models import Country, News
  
  
  class NewsForm(ModelForm):
      class Meta:
          model = News
  
  
  class NewsAdmin(ModelAdmin):
  
      form = NewsForm
  
      search_fields = ['title', 
                       'country__name']
      list_filter = ('country',
                     'active'
                     )
      list_per_page = 30
      list_editable = ('active', )
      list_display = ('title', 
                      'active'
                      )
      list_select_related = True
      prepopulated_fields = {"slug": ("title",)}
  
  admin.site.register(Country)
  admin.site.register(News, NewsAdmin)
  </code></pre>