Comment 5 for bug 114930

I was also having this problem, but I fixed it by adding '--with-python=/usr/bin/python' to the configure flags. Seems both Python 2.4 and 2.5 are installed and it was getting built against 2.4.

Here is what I did to build a deb package (if anyone is interested):
apt-get source python-clearsilver
apt-get build-dep python-clearsilver
cd clearsilver-0.10.4
nano -w debian/rules # Add '--with-python=/usr/bin/python \' to the DEB_CONFIGURE_EXTRA_FLAGS, save and exit
dpkg-buildpackage -rfakeroot -uc -b
cd ..
sudo dpkg -i python-clearsilver_0.10.4-1ubuntu1_i386.deb