Import Error in python when non root user

Question

I am having an issue which has been driving me crazy. I am trying to run a python script as a non root user but when I try to execute the script I get the following error.

Traceback (most recent call last):
File "/usr/local/lib/EdgarRenderer/src/EdgarRenderer.py", line 13, in <module>
from arelle import PythonUtil  # define 2.x or 3.x string types
ImportError: cannot import name PythonUtil

Now if I execute it as the root user it runs with out a hitch. I have triple checked all permissions and all the scripts and folders access by the desired user are in fact owned by that user (with the exception of the /usr/bin/python3.3 file). This is the command I am trying to execute

su - tomcat -c '/usr/bin/python3.3 /usr/local/lib/EdgarRenderer/src/EdgarRenderer.py -c /usr/local/lib/EdgarRenderer/conf/RunEdgar.xml --xdgConfigHome=/usr/local/lib/re3/arelle'

I run the exact same script the exact same way on another server with out any errors. I am using CentOS 6.5

Thanks!