Setting up Apache and Python WSGI to use VirtualEn

I'm having trouble getting Apache/WSGI to use my VirtualEnv. I have added the following two lines (path on server is pointing to the actual location of site-packages in the target virtualenv) to my WSGI file:

import site
site.addsitedir('/sites/mysite/virtpy/lib/python2.6/site-packages')

(from http://www.foxhop.net/django-virtualenv-apache-mod_wsgi). However, when I try to load the url in the browser I get a 500. Checking the apache logs:

 [Sun Jul 17 11:07:11 2011] [error] [client 94.170.105.142]     app =   import_module(appname)
[Sun Jul 17 11:07:11 2011] [error] [client 94.170.105.142]   File "/usr/local/lib/python2.6/dist-packages/django/utils/importlib.py", line 35, in import_module
[Sun Jul 17 11:07:11 2011] [error] [client 94.170.105.142]     __import__(name)
[Sun Jul 17 11:07:11 2011] [error] [client 94.170.105.142] TemplateSyntaxError: Caught ImportError while rendering: No module named tagging
[Sun Jul 17 11:07:11 2011] [debug] mod_deflate.c(615): [client 94.170.105.142] Zlib: Compressed 629 to 387 : URL /

So I guess that the VirtualEnv isn't being loaded. Anyone know how to tell Apache / WSGI the correct virtualenv to use?

UPDATE

I have updated django.wsgi following Ken's advice, but now I am getting the following error in the apache log

[Sun Jul 17 16:46:36 2011] [info] [client 94.170.105.142] mod_wsgi (pid=11260, process='', application='igniteflow-django.com:8090|'): Loading WSGI script '/sites/igniteflow/apache/django.wsgi'.
[Sun Jul 17 16:46:36 2011] [error] [client 94.170.105.142] mod_wsgi (pid=11260): Target WSGI script '/sites/igniteflow/apache/django.wsgi' cannot be loaded as Python module.
[Sun Jul 17 16:46:36 2011] [error] [client 94.170.105.142] mod_wsgi (pid=11260): Exception occurred processing WSGI script '/sites/igniteflow/apache/django.wsgi'.
[Sun Jul 17 16:46:36 2011] [error] [client 94.170.106.142] Traceback (most recent call last):
[Sun Jul 17 16:46:36 2011] [error] [client 94.170.105.142]   File "/sites/igniteflow/apache/django.wsgi", line 5, in <module>
[Sun Jul 17 16:46:36 2011] [error] [client 94.170.105.142]     execfile(activate_this, dict(__file__=activate_this))
[Sun Jul 17 16:46:36 2011] [error] [client 94.170.105.142] IOError: [Errno 13] Permission denied: '/root/.virtualenvs/igniteflow/bin/activate_this.py'

I assume this is because the virtualenv is in root and apache doesn't have permissions? I chowned the folder to root:www-data but it hasn't fixed the problem. Any suggestions?

In my app.wsgi file I have something like this. You will need to change it to put to where your virtual env is located, mine is under /opt/ve/ve_name/ in this example.

import os
# activate virtualenv
activate_this = os.path.expanduser("/opt/ve/ve_name/bin/activate_this.py")
execfile(activate_this, dict(__file__=activate_this))