krb5_auth gem is always required in a source install
Now that lib/gitlab/kerberos/authentication.rb
is eager loaded, this require statement forces all source installers to include this module even if kerberos.enabled = false
in the config.
One possible solution would be to check the setting before attempting to load and define this module, although I'm not sure if the settings are available during the eager load. Perhaps we can just try/rescue if the module does not exist or move the require
inside the constructor.