'Create a new security group.
:keyword description: security group description
:type description: ``unicode``
:keyword client_token: a token generated by client to identify
each request.
:type client_token: ``str``'

def ex_create_security_group(self, description=None, client_token=None):

    params = {'Action': 'CreateSecurityGroup', 'RegionId': self.region}
    if description:
        params['Description'] = description
    if client_token:
        params['ClientToken'] = client_token
    resp = self.connection.request(self.path, params)
    return findtext(resp.object, 'SecurityGroupId', namespace=self.namespace)
