def verifyHostKey(transport, host, pubKey, fingerprint):
    """
    Verify a host's key.

    This function is a gross vestige of some bad factoring in the client
    internals.  The actual implementation, and a better signature of this logic
    is in L{KnownHostsFile.verifyHostKey}.  This function is not deprecated yet
    because the callers have not yet been rehabilitated, but they should
    eventually be changed to call that method instead.

    However, this function does perform two functions not implemented by
    L{KnownHostsFile.verifyHostKey}.  It determines the path to the user's
    known_hosts file based on the options (which should really be the options
    object's job), and it provides an opener to L{ConsoleUI} which opens
    '/dev/tty' so that the user will be prompted on the tty of the process even
    if the input and output of the process has been redirected.  This latter
    part is, somewhat obviously, not portable, but I don't know of a portable
    equivalent that could be used.

    @param host: Due to a bug in L{SSHClientTransport.verifyHostKey}, this is
    always the dotted-quad IP address of the host being connected to.
    @type host: L{str}

    @param transport: the client transport which is attempting to connect to
    the given host.
    @type transport: L{SSHClientTransport}

    @param fingerprint: the fingerprint of the given public key, in
    xx:xx:xx:... format.  This is ignored in favor of getting the fingerprint
    from the key itself.
    @type fingerprint: L{str}

    @param pubKey: The public key of the server being connected to.
    @type pubKey: L{str}

    @return: a L{Deferred} which fires with C{1} if the key was successfully
    verified, or fails if the key could not be successfully verified.  Failure
    types may include L{HostKeyChanged}, L{UserRejectedKey}, L{IOError} or
    L{KeyboardInterrupt}.
    """
    actualHost = transport.factory.options['host']
    actualKey = keys.Key.fromString(pubKey)
    kh = KnownHostsFile.fromPath(FilePath(
            transport.factory.options['known-hosts']
            or os.path.expanduser(_KNOWN_HOSTS)
            ))
    ui = ConsoleUI(lambda : _open("/dev/tty", "r+b", buffering=0))
    return kh.verifyHostKey(ui, actualHost, host, actualKey)

    Verify a host's key.

    This function is a gross vestige of some bad factoring in the client
    internals.  The actual implementation, and a better signature of this logic
    is in L{KnownHostsFile.verifyHostKey}.  This function is not deprecated yet
    because the callers have not yet been rehabilitated, but they should
    eventually be changed to call that method instead.

    However, this function does perform two functions not implemented by
    L{KnownHostsFile.verifyHostKey}.  It determines the path to the user's
    known_hosts file based on the options (which should really be the options
    object's job), and it provides an opener to L{ConsoleUI} which opens
    '/dev/tty' so that the user will be prompted on the tty of the process even
    if the input and output of the process has been redirected.  This latter
    part is, somewhat obviously, not portable, but I don't know of a portable
    equivalent that could be used.

    @param host: Due to a bug in L{SSHClientTransport.verifyHostKey}, this is
    always the dotted-quad IP address of the host being connected to.
    @type host: L{str}

    @param transport: the client transport which is attempting to connect to
    the given host.
    @type transport: L{SSHClientTransport}

    @param fingerprint: the fingerprint of the given public key, in
    xx:xx:xx:... format.  This is ignored in favor of getting the fingerprint
    from the key itself.
    @type fingerprint: L{str}

    @param pubKey: The public key of the server being connected to.
    @type pubKey: L{str}

    @return: a L{Deferred} which fires with C{1} if the key was successfully
    verified, or fails if the key could not be successfully verified.  Failure
    types may include L{HostKeyChanged}, L{UserRejectedKey}, L{IOError} or
    L{KeyboardInterrupt}.
    
stackoverflow/venv/lib/python3.6/site-packages/twisted/conch/client/default.py