I don't think this `if` is doing what you want.  It's still assuming that settings.PAID_COURSE_REGISTRATION_CURRENCY exists, just testing that it's not None or ''.  You might as well forgo the conditional and just rely on defaults in the setting. (lms/envs/common.py defaults to ["usd", "$"] for this setting)

try using `getattr(settings, 'PAID_COURSE_REGISTRATION_CURRENCY')` or something similar