os.fork raises AttributeError, not NameError, if fork() isn't

supported.  Pointed out by Moshe Zadka <moshez@math.huji.ac.il>.

Lib/CGIHTTPServer.py

@@ -21,7 +21,7 @@ import SimpleHTTPServer
 
 try:
     os.fork
-except NameError:
+except AttributeError:
     raise SystemError, __name__ + " requires os.fork()"