ImportError: libifsql.so: cannot open shared object file: No such file or directory

I installed the IBM Informix SDK. It is setup in /opt/IBM/Informix.
I installed Informixdb using this:

python setup.py install --esql-informixdir=/opt/IBM/informix

python setup.py install

The output from python setup.py install:

root@host:/informixdb/InformixDB-2.5# python setup.py install
running install
running build
running build_py
running build_ext
running install_lib
running install_egg_info
Removing /usr/local/lib/python2.7/dist-packages/InformixDB-2.5.egg-info
Writing /usr/local/lib/python2.7/dist-packages/InformixDB-2.5.egg-info

Everything seems okay. So I tried running this:

#!/usr/bin/python
import sys
import informixdb # import the InformixDB module
sys.exit(0);

I keep getting this error:

root@host:/var/www# python informix.py
Traceback (most recent call last):
File "informix.py", line 4, in <module>
import informixdb # import the InformixDB module
File "/usr/local/lib/python2.7/dist-packages/informixdb.py", line 146, in <module>
from _informixdb import *
ImportError: libifsql.so: cannot open shared object file: No such file or directory

I have checked and I see the informixdb.py file:

root@host:/var/www# find / -name informixdb.py
/usr/local/lib/python2.7/dist-packages/informixdb.py
/informixdb/InformixDB-2.5/build/lib.linux-x86_64-2.7/informixdb.py
/informixdb/InformixDB-2.5/informixdb.py

I can find libifsql.so here:

root@host:/var/www# find / -name libifsql.so
/opt/IBM/informix/lib/esql/libifsql.so

I have set INFORMIXDIR:

PATH=$INFORMIXDIR/bin:/opt/IBM/Informix