Python "import" statement fails for any module in /site-packages/ when run by radiusd from example.py

Before I go into exact code, paths, version etc. any general advice or troubleshooting steps for figuring out why python import statement fails to execute for any python library I try to call for from /etc/raddb/mods-config/python/example.py? - example.py runs fine for other python statements - I can do "import sys" and it works fine, but sys is a built in python module - I can execute "import" for any python module defined under /usr/lib/python2.7/site-packages/ in python environment under radiusd users (e.g. sudo -u radiusd python) I am very amateur when it comes to linuz, so please bear with me... Thank you! Gleb Lisikh