Class [warning] RulesPluginFeaturesIntegrationInterface does not exist and could not be loaded faces.inc:233

When upgrading Rules from 7.x-2.11 to 7.x-2.12, SOME sites that use Rules MAY experience the error shown in the title of this issue.

This indicates that you need to rebuild your Drupal registry. Errors of this kind occur often enough in Drupal 7 that a project was created 8 years ago to make this easier to do. The https://www.drupal.org/project/registry_rebuild → project gives you a means of rebuilding the registry either through drush or through the command line. You should have this installed on your site even if you're not affected by this issue; knowing how to rebuild the registry is almost as important a Drupal skill as knowing how to clear the cache.

You may follow the instructions at https://www.drupal.org/project/registry_rebuild → in order to rebuild your registry with or without drush. If you are using drush, an alternate list of 7 steps is shown in comment #8 💬 Class [warning] RulesPluginFeaturesIntegrationInterface does not exist and could not be loaded faces.inc:233 Fixed below

Original issue:

In the email from the cron script reports the following:

array_diff(): Argument #1 is not an array faces.inc:229 [warning]
class_implements(): Class [warning]
RulesPluginFeaturesIntegrationInterface does not exist and
could not be loaded faces.inc:233
PHP Fatal error: Unsupported operand types in /var/www/foto/htdocs/foto-r3.com/sites/all/modules/rules/includes/faces.inc on line 233
Drush command terminated abnormally due to an unrecoverable [error]
error.
Error: Unsupported operand types in
/var/www/foto/htdocs/foto-r3.com/sites/all/modules/rules/includes/faces.inc,
line 233

After the cron I see in Drupal's Recent Log messages:

Warning: array_diff(): Argument #1 is not an array in FacesExtendable->extend() (line 229 of /var/www/foto/htdocs/foto-r3.com/sites/all/modules/rules/includes/faces.inc).

The whole site returns 500 error after the cron job. Since the only option seems to be to revert back to version 2.11, I classify this as Critical.

Please note that I also use elysia_cron on this site.

I will now try to reproduce this in my dev environment.