When updating from 1.3.2 to 1.4 db_migrate will fail with the following message:

root@puppet:/usr/share/foreman# foreman-rake db:migrate
UpdateForemanUrl: migrating =============================================
rake aborted!
An error has occurred, this and all later migrations canceled:

ActiveRecord::ReadOnlyRecord
Tasks: TOP => db:migrate
(See full trace by running task with --trace)

Changing the Foreman URL in /etc/foreman/settings.yaml from

:foreman_url: foreman

to

:foreman_url: https://foreman.*.*

fixes this!