I\'m using Virtualenv with profit on my development environment with web.py, simplejson and other web oriented packages. I\'m going to develop
web.py
simplejson
What worked for me was copying /PyQt4/ and sip.x86_64-linux-gnu.so from /usr/lib/python2.7/dist-packages to /lib/python2.7/site-packages and changing the ownership permissions on these copied files (since the copies were owned by root).
/PyQt4/
sip.x86_64-linux-gnu.so
/usr/lib/python2.7/dist-packages
/lib/python2.7/site-packages