cron can't read PYTHONPATH environment variables?
cron doesn't read shell startup files. You need to explicitly set the environment you need in the crontab or in the script that is being run. You can place variable assignment statements directly in the crontab:
PYTHONPATH=/dir1:/dir2
Each directory you need will have to be listed, because you can't append to it since the previous value isn't available.
Include at the begining of the script.
. [directorypath].bash_profile