docker-zulip: Unable to send mail : django : The SECRET_KEY setting must not be empty

I’m unable to send mail.

I tried running the manage.py send_test_mail as advertised in settings.py:

docker run -it quay.io/galexrt/zulip:1.5.1-2 app:managepy send_test_email user@example.com

But it fails with:

Running manage.py ...
Traceback (most recent call last):
  File "/home/zulip/deployments/current/scripts/lib/log-management-command", line 15, in <module>
    if not os.path.exists(settings.MANAGEMENT_LOG_PATH):
  File "/home/zulip/deployments/current/zulip-venv/lib/python2.7/site-packages/django/conf/__init__.py", line 53, in __getattr__
    self._setup(name)
  File "/home/zulip/deployments/current/zulip-venv/lib/python2.7/site-packages/django/conf/__init__.py", line 41, in _setup
    self._wrapped = Settings(settings_module)
  File "/home/zulip/deployments/current/zulip-venv/lib/python2.7/site-packages/django/conf/__init__.py", line 116, in __init__
    raise ImproperlyConfigured("The SECRET_KEY setting must not be empty.")
django.core.exceptions.ImproperlyConfigured: The SECRET_KEY setting must not be empty.
Traceback (most recent call last):
  File "/home/zulip/deployments/current/manage.py", line 22, in <module>
    " ".join(sys.argv)])
  File "/usr/lib/python2.7/subprocess.py", line 540, in check_call
    raise CalledProcessError(retcode, cmd)

The logs of docker-compose.up says:

zulip_1      | Setting Zulip secrets ...
zulip_1      | Secrets already generated.
zulip_1      | Secret found for "rabbitmq_password".
zulip_1      | Secret found for "email_password".
zulip_1      | Secret found for "secret_key".