REQUIREMENT_ERROR

DbUpdateController::handle in core/modules/system/src/Controller/DbUpdateController.php

Returns a database update page.

drupal_check_module in core/includes/install.inc

Checks a module's requirements.

drupal_verify_profile in core/includes/install.inc

Verifies that all dependencies are met for a given installation profile.

experimental_module_requirements_test_requirements in core/modules/system/tests/modules/experimental_module_requirements_test/experimental_module_requirements_test.install

Implements hook_requirements().

hook_requirements in core/lib/Drupal/Core/Extension/module.api.php

Check installation requirements and do status reporting.

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