title: Django field name length/convention
body: <p>I am not sure if this is a bug, by design or if I have done something wrong. I have run into this on 1.6.2 and 1.6.4</p>
  
  <p>I have some fields in my models like:</p>
  
  <blockquote>
    <p>my_custom_field = models.CharField()</p>
  </blockquote>
  
  <p>In my forms.py, I have:</p>
  
  <blockquote>
    <p>def clean_my_custom_field():</p>
  </blockquote>
  
  <p>It does not get called. There seems to be a problem with having more than one underscore in the field name. I have several that have 2 or 3 underscores in the name. I have changed one to use a single underscore and it worked.</p>
  
  <p>I have started to look at shortening the names, but was wondering if anyone has come across this and has a work around/fix. Would be nice to keep the descriptive names.</p>
  
  <p>Or is it in fact a bug?</p>
  
  <p><strong>UPDATED:</strong></p>
  
  <p>The form is setup fairly basic. One thing to note is that the long field name seems to work in the Admin, but not in the front end form.</p>
  
  <pre><code>class MyBaseForm(forms.ModelForm):
      class Meta:
          model = MyModel
          fields = "__all__"
  
      def clean_active_listing_expiry_date(self):
          print "You are HERE!"
          "Do something else here"
  </code></pre>
  
  <p>UPDATE:</p>
  
  <pre><code>class MyModel(models.Model):
      ... other fields listed before and after of course.
      active_listing_expiry_date = models.DateTimeField(
          verbose_name='Active Expiry Date',
          help_text="Date format: YYYY-MM-DD",
          blank=True,
          null=True
      )
  </code></pre>
  
  <p>UPDATE:</p>
  
  <p>views.py</p>
  
  <pre><code>def residential_add(request, ptype='Residential', template_name='properties/add_residential.html'):
      if request.method == 'POST':
          property_form = ResidentialPropertyForm(request.POST)
  
          if property_form.is_valid():
              print "*" * 60
              print "FORM IS VALID"
  
      else:
          property_form = ResidentialPropertyForm()
  
      return render_to_response(
          template_name,
          {
              'property': property_form,
          },
          context_instance=RequestContext(request)
      )
  </code></pre>