tests: comment the assertion that detects file descriptor leaks

neo/tests/threaded/__init__.py

@@ -142,7 +142,9 @@ class Serialized(object):
 
     @classmethod
     def stop(cls):
-        assert not cls._fd_dict, cls._fd_dict
+        assert not cls._fd_dict, ("file descriptor leak (%r)\nThis may happen"
+            " when a test fails, in which case you can see the real exception"
+            " by disabling this one." % cls._fd_dict)
         del(cls._busy, cls._busy_cond, cls._epoll, cls._fd_dict,
             cls._pdb, cls._sched_lock, cls._tic_lock)
 

neo/tests/threaded/test.py

@@ -1004,11 +1004,13 @@ class Test(NEOThreadedTest):
 
             # modify x with another client
             client = cluster.newClient()
-            txn = transaction.Transaction()
-            client.tpc_begin(txn)
-            client.store(x1._p_oid, x1._p_serial, y, '', txn)
-            tid = client.tpc_finish(txn, None)
-            client.close()
+            try:
+                txn = transaction.Transaction()
+                client.tpc_begin(txn)
+                client.store(x1._p_oid, x1._p_serial, y, '', txn)
+                tid = client.tpc_finish(txn, None)
+            finally:
+                client.close()
             self.tic()
 
             # Check reconnection to storage.