Comment 11 for bug 675014

Oleg: You probably need to call setlocale in your environment for the LANG setting to be picked up.

I can't find much Trac specific on this, but there was a mod_python bug along these lines:
<http://trac.edgewall.org/ticket/764>

And there's some mod_wsgi documentation on such issues:
<http://code.google.com/p/modwsgi/wiki/ApplicationIssues#Timezone_and_Locale_Settings>

You may need to ask on a mod_wsgi or trac list for further support as your current setup (whether you're running in embedded or daemon mode, and what other code the server is using) will matter here.