unicode and os.system

[Dumbkiwi]

I've got a rather large python script that I write and maintain.  It has
some interaction with other programmes on the linux/kde desktop through
the dcop interface.  This script also uses the gettext module to enable
the output of the script to be translated into several languages,
including utf-8 encoded text.

However, when I issue a dcop call to an application (which is a docker
application that can display text above an icon), the operation fails with:

Traceback (most recent call last):
  File "/home/matt/karamba/lwbkup/liquid_weather.py", line 2970, in widgetUpdated
    os.system('dcop kxdocker docker changeTextByName Current "%s : %s"' %(_(situtext), weather.temperature()))
UnicodeDecodeError: 'ascii' codec can't decode byte 0xb0 in position 2:
ordinal not in range(128)

_(situtext) is a variable containing a unicode string.  

My python environment has ascii as its encoding for stdout
>>> import sys
>>> print sys.stdout.encoding
ANSI_X3.4-1968

the dcop call I'm using requires a QString variable where the _(situtext)
is.

Can anyone help me to work through this issue?  I'm a bit lost as to where
to start.

Thanks

Matt