title: Django PasswordResetForm not working when extending it
body: <p>I wanted to make some changes to the default</p>
  
  <p>django.contrib.auth.forms.PasswordResetForm</p>
  
  <p>I did the following:</p>
  
  <pre><code>class CustomPasswordResetForm(PasswordResetForm):
      def is_valid(self):
          ret = forms.Form.is_valid(self)
          for f in self.errors:
              self.fields[f].widget.attrs.update({'class': 'invalid'})
          return ret
      def clean_email(self):
          email = self.cleaned_data.get('email')
          if not User.objects.filter(email=email).exists():
              raise forms.ValidationError('כתובת אימייל זאת לא קיימת במערכת!')
  </code></pre>
  
  <p>nothing to complicated, just added a class for invalid fields and added an error if the email doesn't exist (not sure why this doesn't happen by default tbh)</p>
  
  <p>Also I defined the new form in urls.py</p>
  
  <pre><code>url(r'^password_reset/$', auth_views.password_reset,{'password_reset_form': CustomPasswordResetForm,}, name='password_reset'),
  </code></pre>
  
  <p>both the functions I overrided are working as intended, but the reset password form no longer works, I'm not receiving an email, even though the form passes with no validation errors on to /password_reset/done/</p>