gistfile1.py

import socket

class ImageDownloadFailure(Exception):

    def __init__(self, host, port, path, error):
        self.host = host
        self.port = port
        self.path = path
        msg = ('Failed to download %(path)s from %(host)s:%(port)s: %(error)s'
               % {'host': host, 'port': port, 'path': path, 'error': error})
        super(ImageDownloadFailure, self).__init__(msg)


def download_image(host, port, path):
    try:
        s = socket.create_connection((host, port))
    except socket.error as e:
        raise ImageDownloadFailure(host, port, path, e.strerror)

download_image('localhost', 3366, 'foobar')