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django.core.exceptions.ImproperlyConfigured: The SECRET_KEY setting must not be empty

# add SECRET_KEY from terminal (secret_key is collected from django -->settings.py file)
$ export SECRET_KEY='lmrffsgfhrilklg-za7#57vi!zr)ps8)2anyona25###dl)s-#s=7=vn_'
#settings.py
import os
SECRET_KEY = os.environ['SECRET_KEY']

django.core.exceptions.improperlyconfigured: the secret_key setting must not be empty.

I had the same error and it turned out to be a circular dependency between a module or class loaded by the settings and the settings module itself. In my case it was a middleware class which was named in the settings which itself tried to load the settings.