added comment/suggestion about potential memory leak

eventlet/tpool.py

@@ -74,9 +74,13 @@ def tworker():
             rv = meth(*args,**kwargs)
         except SYS_EXCS:
             raise
-        except Exception,exn:
+        except Exception:
             rv = sys.exc_info()
-        _rspq.put((e,rv))
+        _rspq.put((e,rv))               # @@tavis: not supposed to
+                                        # keep references to
+                                        # sys.exc_info() so it would
+                                        # be worthwhile testing
+                                        # if this leads to memory leaks
         meth = args = kwargs = e = rv = None
         _signal_t2e()