'Transform a single IP address into a network specification by
applying the given netmask.
Returns a new IP instance.
>>> print(IP(\'127.0.0.1\').make_net(\'255.0.0.0\'))
127.0.0.0/8'

def make_net(self, netmask):

    if ('/' in str(netmask)):
        raise ValueError(('invalid    netmask    (%s)' % netmask))
    return IP(('%s/%s' % (self, netmask)), make_net=True)
