DNM - New Vouch Model

No need to add custom clean function just to change the error message. You can use the `error_messages` argument.

```python
description = forms.CharField(
       label=_lazy(u'Provide a reason for vouching with relevant links'),
       widget=forms.Textarea(attrs={'rows': 10, 'cols': 20, 'maxlength': 500}),
       max_length=500
       description = forms.CharField(
        label=_lazy(u'Provide a reason for vouching with relevant links'),
        widget=forms.Textarea(attrs={'rows': 10, 'cols': 20, 'maxlength': 500}),
        max_length=500
        error_messages={'required': _(u'You must enter a reason for vouching for this person.'})
    )
)
```