JSON Encoder crashes on settings with translations: "ValueError: Circular reference detected"

[Kyle Olivo]

Description:

Horizon uses the REST_API_REQUIRED_SETTINGS key in the local_settings.py configuration file In order to make the contained configuration available to the the client side angular code.

Some configurations include ugettext objects which fail to serialize when passing through http.

eg.
OPENSTACK_IMAGE_BACKEND = {
    'image_formats': [
        ('aki', _('AKI - Amazon Kernel Image'))
    ]
}

Steps to Reproduce:
* Add 'OPENSTACK_IMAGE_BACKEND' to the 'REST_API_REQUIRED_SETTINGS' key in the local_settings.py.
* call the settings endpoint: http://localhost:8000/api/settings
* Django throws a 500 server exception with the following stack trace: see attached

Impact:
As a workaround, we are setting configuration settings as constants, instead of getting it from the settings service. See
https://review.openstack.org/#/c/236042/22/openstack_dashboard/static/app/core/images/images.module.js

[Rob Cresswell (robcresswell-deactivatedaccount)]

I've come across this exact error recently, but not entirely sure how it is triggered.

[Rob Cresswell (robcresswell-deactivatedaccount)]

Marked Medium because it doesn't currently cause errors within Horizon, but certainly could prevent proper usage by plugins.

[Matt Borland (palecrow)]

See the changes to settings.py in: https://review.openstack.org/#/c/217828/

I believe this now fixes this specific problem because as the comments show, the exposed object no longer contains lazy-loaded gettext objects. It contains only the keys themselves, which are just strings.

I believe this can be closed. Can anyone concur?

[Matt Borland (palecrow)]

Rob concurred on IRC.