You need to export environment variables for child processes to see them:
export SECRET_KEY
Demo:
$ SECRET_KEY='foobar'
$ bin/python -c "import os; print os.environ.get('SECRET_KEY', 'Nonesuch')"
Nonesuch
$ export SECRET_KEY
$ bin/python -c "import os; print os.environ.get('SECRET_KEY', 'Nonesuch')"
foobar
You can combine the setting and exporting in one step:
export SECRET_KEY=xxx-xxx-xxxx
Note that new variables in /etc/environment do not show up in your existing shells automatically, not until you have a new login. For a GUI desktop, you’ll have to log out and log in again, for SSH sessions you’ll have to create a new SSH login. Only then will you get a new tree of processes with the changes present. Using source /etc/environment only sets ‘local’ variables (the file is not a script). See How to reload /etc/environment without rebooting? over on Super User.