"sendmail" not available, possible regression

Moving to the intended project.

We can adopt the official image approach https://github.com/docker-library/php/issues/135

We can see how scheduler started to fail on Dec 9th: https://git.drupalcode.org/project/scheduler/-/pipelines?page=1&scope=al...
And I just tried api and see the same: https://git.drupalcode.org/project/api/-/pipelines?page=1&scope=all&ref=...

Both modules started to fail with the same error and with no changes.

sh: 1: -t: not found
WD mail: Error sending e-mail (from admin@example.com to             [error]
admin@example.com).

Unable to send e-mail. Contact the site administrator if the problem [error]
persists.

It might be that we never discovered this because of the drush version that the images use. Some drush versions do not fail hard whereas some others do. In this case we're talking about two different drush versions utilized for Drupal 7.

From the drush docs (https://drushcommands.com/drush-8x/core/site-install/):

// Disable email notification during install and later (D7). If your server has no mail transfer agent, this gets rid of an error during install.
drush site-install standard install_configure_form.update_status_module='array(FALSE,FALSE)'

Note that this fixes the issue: https://git.drupalcode.org/issue/scheduler-3387331/-/jobs/483425

We can work around it using those options, but the issue might remains on "sendmail" (or similar) not being available.
So at this point it could be a "feature request" or a "won't fix works as designed" I guess.

Thanks fjgarlin for the commit. I confirm that the main branch of Scheduler 7.x passes again now.

You talked about drush version, but it is the same 8.4.12 in both the failing job and the previously passing job.

I was talking about the "drush" version used for core (uses "drush" from the image) vs contrib (uses "drush" brought via composer).

OK. In the phpunit 'context' status report, it shows 8.4.12, and in the composer step it shows 8.4.12. Which one is that, and how can we see the other version number?

All those 8.4.12 are coming from contrib. There is no drush st run in core, but you can see that it is version 8.3.5 here https://git.drupalcode.org/project/drupalci_environments/-/blob/dev/php/...

Thanks for the explanation. The images and docker files are on the edge of my current understanding (which makes one feel de-skilled and floundering) but I am always ready to try to learn new things.