'Convert back into a valid zone object.'

def clean_zone(self):

    zone_id = self.cleaned_data['zone']
    if (zone_id not in [tup[0] for tup in self.fields['zone'].choices]):
        raise forms.ValidationError(_('You    must    select    a    sharing    network    from    the    given    choices.'))
    try:
        zone = Zone.objects.get(id=zone_id)
    except:
        raise forms.ValidationError(_('You    must    select    a    valid    sharing    network.'))
    return zone
