reverse() argument after ** must be a mapping

I have an inscription form that doesn't work when submitting.

I get this error:

reverse() argument after ** must be a mapping, not str**

This is my view:

def inscription(request, seance_id):
    seance = get_object_or_404(Variant, id=seance_id)
    inscription_config = {'form_class': InscriptionForm,
                          'extra_context': {'seance': seance}}    

    return create_object(request, **inscription_config)

My form:

class InscriptionForm(forms.ModelForm):
    class Meta:
        model = Inscription
        
    def clean(self):
        cleaned_data = self.cleaned_data
        email = cleaned_data.get("mail")
        mail_confirmation = cleaned_data.get("mail_confirmation")
    
        if email != mail_confirmation:
            raise forms.ValidationError("Les deux adresses mails doivent correspondre")
    
        return cleaned_data

Seems what triggering the error is inscription_config in the return statement, but I have no idea why.

EDIT

Environment:

Request Method: POST Request URL: http://127.0.0.1:8039/formations/inscription/1/ Django Version: 1.2.5 Python Version: 2.7.2 Installed Applications: ['django.contrib.auth', 'django.contrib.comments', 'django.contrib.contenttypes', 'django.contrib.sessions', 'django.contrib.sites', 'django.contrib.messages', 'django.contrib.admin', 'ckeditor', 'constance', 'constance.backends.database', 'custom_flatpages', 'django_extensions', 'django_mobile', 'django_xmlrpc', 'easy_thumbnails', 'gestion_formations', 'file_uploader', 'less', 'mptt', 'contact', 'newsletter', 'pagination', 'south', 'sentry', 'sentry.client', 'indexer', 'paging', 'contentadmin', 'gallerie'] Installed Middleware: ('annoying.midd