Error 500 when trying to get configs.json

When getting configs.json (on mail.bitmask and cdev.bitmask), the following error appears:

cat providers/mail.bitmask.net/configs.json                                                                                                                            

500 Internal Server Error
If you are the administrator of this website, then please read this web application's log file and/or the web server's log file to find out what went wrong.

(the request has been made with the authentication token)

(from redmine: created on 2016-02-17, closed on 2016-02-24)