gistfile1.txt

import urllib
import os.path

with open('skins.txt') as fp:
    for line in fp:
        try:
            print line
            if not (os.path.isfile("skins/" + line.rstrip() + ".png")): {
                urllib.urlretrieve("http://158.69.120.5/assets/php/avatar.php?u=" + line.rstrip() + "&s=16", "skins/" + line.rstrip() + ".png")
            }
        except:
            pass