backport of the checkin of revision 1.36 of asyncore.py

On Windows, select() does not accept empty lists.
Patch suggested by Guido, fixes SF item 611464.

Bugfix candidate, will backport to release22-maint myself.

Lib/asyncore.py

@@ -50,6 +50,7 @@ import exceptions
 import select
 import socket
 import sys
+import time
 
 import os
 from errno import EALREADY, EINPROGRESS, EWOULDBLOCK, ECONNRESET, \
@@ -75,12 +76,15 @@ def poll (timeout=0.0, map=None):
                 r.append (fd)
             if obj.writable():
                 w.append (fd)
-        try:
-            r,w,e = select.select (r,w,e, timeout)
-        except select.error, err:
-            if err[0] != EINTR:
-                raise
-            r = []; w = []; e = []
+        if [] == r == w == e:
+            time.sleep(timeout)
+        else:
+            try:
+                r,w,e = select.select (r,w,e, timeout)
+            except select.error, err:
+                if err[0] != EINTR:
+                    raise
+                r = []; w = []; e = []
 
         if DEBUG:
             print r,w,e