Explicitly close the socket and temp file in URLopener.retrieve(), so

that multiple retrievals using the same connection will work.

This leaves open the more general problem that after
    f = urlopen("ftp://...")
f must be closed before another retrieval from the same host should be
attempted.

Lib/urllib.py

@@ -191,6 +191,8 @@ class URLopener:
 		while block:
 			tfp.write(block)
 			block = fp.read(bs)
+		fp.close()
+		tfp.close()
 		del fp
 		del tfp
 		return result