In the activate_this.py script:
site_packages = os.path.join(base, 'lib', 'python%s' % sys.version[:3], 'site-packages')
It uses sys.version[:3] and this evaluates to python2.6 (the system default). But I had installed python2.7 and created my virtualenv with:
virtualenv -p /usr/local/bin/python2.7 venv
How do I make virtualenv work with the correct version of python?
Creating a symlink from /usr/bin/python to /usr/local/bin/python2.7 is not a solution because the CentOS system depends on python2.6.