Subtle change to run() loop: when a deadlock is detected, set

_deadline to None, to prevent reporting the same timeout more than
once.  Added a helpful comment too. :-)

src/ZEO/StorageServer.py

@@ -824,9 +824,12 @@ class TimeoutThread(threading.Thread):
         while 1:
             self._cond.acquire()
             try:
-                while self._client is None:
+                while self._deadline is None:
                     self._cond.wait()
                 howlong = self._deadline - time.time()
+                if howlong <= 0:
+                    # Prevent reporting timeout more than once
+                    self._deadline = None
                 client = self._client # For the howlong <= 0 branch below
             finally:
                 self._cond.release()