Try using a wrapper script. The one described in the answer you link to is possibly more complex than what's needed for lookups. I solved this problem yesterday using a wrapper, as follows.
wrapper.py:
import os
NEW_PYTHON_PATH = '/usr/bin/python'
os.environ['PYTHONPATH'] = NEW_PYTHON_PATH
my_process = '/opt/splunk/etc/apps/zgp/bin/lookup.py')
os.execv(my_process, ())
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