Question about FutureWarning

[Steven W. Orr]

I have module M1 which has the following line in it:

   StartTime   = safe_dict_get ( dic, 'starttime', 0xFFFFFFFF )

It gets imported by modules M2 and M3. And finally, M4 imports both M2 and 
M3.

M4
  |\M3
  | |\M1
  |\M2
  | |\M1

I'm building a .deb file which means I have to compile the modules into 
.pyc and .pyo files.

The compile command I use is

python=/usr/bin/python2.3
i_python ()
{
     $python -c "import $1"
     $python -O -c "import $1"
}
i_python M1
i_python M2
i_python M3
i_python M4

When M1 is compiled, there's no problem. The same for when I compile M2 
and M3. But when M4 is compiled, I get the following message:

M1.py:268: FutureWarning: hex/oct constants > sys.maxint will 
return positive values in Python 2.4 and up
   StartTime   = safe_dict_get ( dic, 'starttime', 0xFFFFFFFF )

I get the message twice, ostensibly because of M3 and M2.

I was able to shut off the warning by adding the following lines *before* 
the import in M4.

import warnings
warnings.filterwarnings('ignore', category=FutureWarning)

My question is this: Why can the warning not be shut off by putting the 
two lines in M1?

TIA

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