monkey: avoid spurious warnings

gevent/monkey.py

@@ -15,10 +15,9 @@ def patch_time():
     _time.sleep = sleep
 
 def patch_thread():
-    if noisy and 'threading' in sys.modules:
-        sys.stderr.write("gevent.monkey's warning: 'threading' is already imported\n\n")
     from gevent import thread as green_thread
     thread = __import__('thread')
+    if thread.exit is not green_thread.exit:
         thread.get_ident = green_thread.get_ident
         thread.start_new_thread = green_thread.start_new_thread
         thread.LockType = green_thread.LockType
@@ -26,6 +25,8 @@ def patch_thread():
         thread.exit = green_thread.exit
         if hasattr(green_thread, 'stack_size'):
             thread.stack_size = green_thread.stack_size
+        if noisy and 'threading' in sys.modules:
+            sys.stderr.write("gevent.monkey's warning: 'threading' is already imported\n\n")
         # built-in thread._local object won't work as greenlet-local
         if '_threading_local' not in sys.modules:
             import _threading_local