The problem was with the cssselect installation. For some unidentified reason the cssselect package was installed to /root/.local/lib/python2.7/site-packages/ instead of /usr/local/lib/python2.7/dist-packages/.
Cssselect was installed with pip install cssselect
on Debian GNU/Linux 7.4 (wheezy, Linux 3.2.0-4-amd64 x86_64). Don't know if it was just some weird typo of mine, or a bug.
The solution was to uninstall cssselect and reinstall it. This time it went to correct place and everything works as before. There was no need to modify python code at all.
Ty, for you answers ;)