Added logic to avoid spurious errors from the logging system on exit.

NEWS.txt

-What's new on ZODB 3.7.0b3?
+
+What's new on ZODB 3.7.0b4?
 ===========================
 
 Packaging
@@ -19,6 +20,9 @@ Packaging
 ClientStorage
 -------------
 
+- (3.7b4) Added logic to avoid spurious errors from the logging system
+  on exit.
+
 - (3.7b2) Removed the "sync" mode for ClientStorage.  
 
   Previously, a ClientStorage could be in either "sync" mode or "async"

src/ZEO/zrpc/connection.py

@@ -12,6 +12,7 @@
 #
 ##############################################################################
 import asyncore
+import atexit
 import errno
 import select
 import sys
@@ -39,6 +40,7 @@ client_timeout_count = 0 # for testing
 client_map = {}
 client_trigger = trigger(client_map)
 client_logger = logging.getLogger('ZEO.zrpc.client_loop')
+atexit.register(client_map.clear)
 
 def client_loop():
     map = client_map
@@ -106,17 +108,25 @@ def client_loop():
                 _exception(obj)
 
         except:
-            client_logger.critical('The ZEO cient loop failed.',
-                            exc_info=sys.exc_info())
-            for fd, obj in map.items():
-                if obj is client_trigger:
-                    continue
+            if map:
                 try:
-                    obj.mgr.client.close()
-                except:
-                    map.pop(fd, None)
-                    client_logger.critical("Couldn't close a dispatcher.",
+                    client_logger.critical('The ZEO cient loop failed.',
                                            exc_info=sys.exc_info())
+                except:
+                    pass
+
+                for fd, obj in map.items():
+                    if obj is client_trigger:
+                        continue
+                    try:
+                        obj.mgr.client.close()
+                    except:
+                        map.pop(fd, None)
+                        try:
+                            client_logger.critical("Couldn't close a dispatcher.",
+                                                   exc_info=sys.exc_info())
+                        except:
+                            pass
 
 client_thread = threading.Thread(target=client_loop)
 client_thread.setDaemon(True)