Functional tests fail due to missing schema

Problem/Motivation

All functional tests from any module will fail if Bootstrap4 OR a sub-theme is installed. This is due to this theme missing a schema.yml file

There was 1 error:

1) Drupal\mortgages\Tests\Functional\MortgageCalculatorFunctionalTest::testMortgageCalc
Drupal\Core\Config\Schema\SchemaIncompleteException: No schema for bootstrap4.settings

/app/web/core/lib/Drupal/Core/Config/Development/ConfigSchemaChecker.php:88
/app/web/core/lib/Drupal/Component/EventDispatcher/ContainerAwareEventDispatcher.php:111
/app/web/core/lib/Drupal/Core/Config/Config.php:231
/app/web/core/lib/Drupal/Core/Config/ConfigInstaller.php:380
/app/web/core/lib/Drupal/Core/Config/ConfigInstaller.php:137
/app/web/core/lib/Drupal/Core/ProxyClass/Config/ConfigInstaller.php:75
/app/web/core/lib/Drupal/Core/Extension/ThemeInstaller.php:232
/app/web/core/lib/Drupal/Core/Test/FunctionalTestSetupTrait.php:430
/app/web/core/tests/Drupal/Tests/BrowserTestBase.php:580
/app/web/core/tests/Drupal/Tests/BrowserTestBase.php:400
/app/web/modules/custom/mortgages/src/Tests/src/Functional/MortgageCalculatorFunctionalTest.php:23
/app/vendor/phpunit/phpunit/src/Framework/TestResult.php:691

Steps to reproduce

Run any functional test

Proposed resolution

Patch attached that simply adds the schema file