18     if not host.boot:

    18     for bootopt in ('next-server', 'filename'):

    19         next_server = filename = None

    19         if bootopt in host.boot:

    20     elif host.boot.startswith('/'):

    20             yield bootopt, host.boot[bootopt]

    21         next_server = None

    22         filename = host.boot[1:]

    23     elif host.boot.endswith(':'):

    24         next_server = host.boot[:-1]

    25         filename = None

    26     elif ':' in host.boot :

    27         next_server, filename = host.boot.split(':', 1)

    28     else :

    29         raise HostError(host, "invalid boot={host.boot}".format(host=host))

    30 

    31     if next_server:

    32         yield 'next-server', next_server

    33     

    34     if filename:

    35         yield 'filename', filename