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user_id=9205

the shift op still prints a warning:
>>> 0xffff000 << 4
/home/calvin/.python:1: FutureWarning: x<<y losing bits or
changing sign will return a long in Python 2.4 and up
  from __future__ import nested_scopes
-65536

Writing explicitely the above negative value in
portalocker.py does not print the warning, and seems to work
(I executed "python2.3.exe portalocker.py" for test).