On my local machine, I run a python script which contains this line
bashCommand = \"cwm --rdf test.rdf --ntriples > test.nt\" os.system(bashCommand)
According to the error you are missing a package named swap on the server. This /usr/bin/cwm requires it. If you're on Ubuntu/Debian, install python-swap using aptitude.
/usr/bin/cwm
python-swap