'Return a single extra spec item.'

@wsgi.Controller.api_version('3.11')
def show(self, req, group_type_id, id):

    context = req.environ['cinder.context']
    self._check_policy(context)
    self._check_type(context, group_type_id)
    specs = self._get_group_specs(context, group_type_id)
    if (id in specs['group_specs']):
        return {id: specs['group_specs'][id]}
    else:
        msg = (_('Group    Type    %(type_id)s    has    no    extra    spec    with    key    %(id)s.') % {'type_id': group_type_id, 'id': id})
        raise webob.exc.HTTPNotFound(explanation=msg)
