[999484] Django error when running --list-dependencies

I get the following error when building an unstable vagrant box with build dependencies included.

The command I used to build:

sudo python3 -m freedommaker vagrant \
	 --with-build-dep \
	 --image-size 16G \
	 --build-mirror "$BUILD_MIRROR" \
	 --build-in-ram \
	 2>&1 | tee fm_vagrant_build.log

Error log:

2021-11-09 18:36:39,659 - INFO - Executing command - (['chroot', '/tmp/tmpke0nbwgt', 'bash', '-c', 'apt-get install --no-upgrade --yes   $(/tmp/freedombox/run --develop --list-dependencies)'],) {}
2021-11-09 18:36:39,659 - DEBUG - run external command: [['chroot', '/tmp/tmpke0nbwgt', 'bash', '-c', 'apt-get install --no-upgrade --yes   $(/tmp/freedombox/run --develop --list-dependencies)']]
2021-11-09 18:36:40,273 - DEBUG - 2> Traceback (most recent call last):
  File "/tmp/freedombox/run", line 8, in <module>
2021-11-09 18:36:40,273 - DEBUG - 2> plinth.__main__.main()
  File "/tmp/freedombox/plinth/__main__.py", line 112, in main
    module_loader.include_urls()
  File "/tmp/freedombox/plinth/module_loader.py", line 28, in include_urls
    _include_module_urls(module_import_path, module_name)
  File "/tmp/freedombox/plinth/module_loader.py", line 108, in _include_module_urls
    from plinth import urls
  File "/tmp/freedombox/plinth/urls.py", line 9, in <module>
    from plinth.modules.sso.views import CaptchaLoginView
  File "/tmp/freedombox/plinth/modules/sso/views.py", line 13, in <module>
    from django.contrib.auth.views import LoginView, LogoutView
  File "/usr/lib/python3/dist-packages/django/contrib/auth/views.py", line 10, in <module>
    from django.contrib.auth.forms import (
  File "/usr/lib/python3/dist-packages/django/contrib/auth/forms.py", line 11, in <module>
2021-11-09 18:36:40,273 - DEBUG - 2> from django.contrib.auth.tokens import default_token_generator
  File "/usr/lib/python3/dist-packages/django/contrib/auth/tokens.py", line 117, in <module>
    default_token_generator = PasswordResetTokenGenerator()
  File "/usr/lib/python3/dist-packages/django/contrib/auth/tokens.py", line 18, in __init__
2021-11-09 18:36:40,273 - DEBUG - 2> self.secret = self.secret or settings.SECRET_KEY
  File "/usr/lib/python3/dist-packages/django/conf/__init__.py", line 90, in __getattr__
    raise ImproperlyConfigured("The SECRET_KEY setting must not be empty.")
django.core.exceptions.ImproperlyConfigured: The SECRET_KEY setting must not be empty.