That error message indicates that your python or some library is too new for SL.
The bitmessage wiki also recommends python 2.7 rather than 3.3.
And python.org reports some issues with 3.3:
Some existing third-party software is not yet compatible with Python 3; if you need to use such software, you can download Python 2.7.x instead.


Anyway, I am using 2.7 from
http://www.python.org/download/releases/2.7.5
and PyQtX from
http://sourceforge.net/projects/pyqtx/