Bug #635453 reports that when you use urllib.urlretrieve() to read from an FTP server and the file you are trying to get does not have the proper permissions for you, you are given a listing of the directory instead of an exception (this is all done by Lib/urllib.py:752).
Now this doesn't make sense to me and I suspect most people would agree. But having that explicit line there on top of it having been in the file since it was renamed from urlopen way backin 1994 makes me hesitate before I delete the line.
Anyone have issues if I ditch the line so an exception is raised instead of getting a directory listing instead?
If you remove this, you won't be able to get a directory listing of directories. I tried this with and without the line; with that line in, it gives a directlry listing, without it gives an IOError (Not a regular file):
urllib.urlretrieve("ftp://ftp.python.org/pub", "xyzzy")
So I'd be against deleting this, unless there's a different way to get directory listings. --Guido van Rossum (home page: http://www.python.org/~guido/)