Error: Failed opening required 'compress.zlib:///builds/project/entity_pager/web/core/modules/system/tests/fixtures/update/drupal-9.3.0.bare.standard.php.gz'

I may be totally wrong here, but

Failed opening required 'compress.zlib:///builds/project/entity_pager/web/core/modules/system/tests/fixtures/update/drupal-9.3.0.bare.standard.php.gz

sounds like you are using files from the core system module, so do you need drupal/system in your composer require-dev as a test dependency?

That pipeline is testing Drupal 11.0.8 and that version does not have that file: https://git.drupalcode.org/project/drupal/-/tree/11.0.8/core/modules/sys...

So the question is, why is the test trying to download that one? That seems to be module specific I guess.

Confirmed, it's hardcoded into the module here: https://git.drupalcode.org/project/entity_pager/-/blob/2.0.x/tests/src/F...

Thanks for doing the research. I did not have time this morning to look at the pipeline in detail or into the project's source. But it did not sound like a Gitlab Templates problem. Therefore I've changed the category to a normal support request, instead of major bug :-)