'Get the value for a `ConfigView`.
May raise a `NotFoundError` if the value is missing (and the
template requires it) or a `ConfigValueError` for invalid values.'

def value(self, view, template=None):

    if view.exists():
        (value, _) = view.first()
        return self.convert(value, view)
    elif (self.default is REQUIRED):
        raise NotFoundError(u'{0}    not    found'.format(view.name))
    else:
        return self.default
