Issue #3117330 by longwave, tedbow, xjm: Trigger errors in deprecated theme functions

core/lib/Drupal/Core/Theme/Registry.php

@@ -495,7 +495,7 @@ protected function processExtension(array &$cache, $name, $type, $theme, $path)
         // if the theme hook specifies a function callback instead, check to
         // ensure the function actually exists.
         if (isset($info['function'])) {
-          @trigger_error(sprintf('Theme functions are deprecated in drupal:8.0.0 and are removed from drupal:10.0.0. Use Twig templates instead of %s(). See https://www.drupal.org/node/1831138', $info['function']), E_USER_DEPRECATED);
+          trigger_error(sprintf('Theme functions are deprecated in drupal:8.0.0 and are removed from drupal:10.0.0. Use Twig templates instead of %s(). See https://www.drupal.org/node/1831138', $info['function']), E_USER_DEPRECATED);
           if (!function_exists($info['function'])) {
             throw new \BadFunctionCallException(sprintf(
               'Theme hook "%s" refers to a theme function callback that does not exist: "%s"',

core/tests/Drupal/KernelTests/Core/Theme/RegistryLegacyTest.php

@@ -27,7 +27,7 @@ class RegistryLegacyTest extends KernelTestBase {
   /**
    * Tests the theme registry with theme functions and multiple subthemes.
    *
-   * @expectedDeprecation Theme functions are deprecated in drupal:8.0.0 and are removed from drupal:10.0.0. Use Twig templates instead of theme_theme_test(). See https://www.drupal.org/node/1831138
+   * @expectedDeprecation Unsilenced deprecation: Theme functions are deprecated in drupal:8.0.0 and are removed from drupal:10.0.0. Use Twig templates instead of theme_theme_test(). See https://www.drupal.org/node/1831138
    */
   public function testMultipleSubThemes() {
     $theme_handler = \Drupal::service('theme_handler');
@@ -47,7 +47,7 @@ public function testMultipleSubThemes() {
   /**
    * Tests the theme registry with theme functions with suggestions.
    *
-   * @expectedDeprecation Theme functions are deprecated in drupal:8.0.0 and are removed from drupal:10.0.0. Use Twig templates instead of test_legacy_theme_theme_test_preprocess_suggestions__kitten__meerkat(). See https://www.drupal.org/node/1831138
+   * @expectedDeprecation Unsilenced deprecation: Theme functions are deprecated in drupal:8.0.0 and are removed from drupal:10.0.0. Use Twig templates instead of test_legacy_theme_theme_test_preprocess_suggestions__kitten__meerkat(). See https://www.drupal.org/node/1831138
    */
   public function testSuggestionPreprocessFunctions() {
     $theme_handler = \Drupal::service('theme_handler');

core/tests/Drupal/Tests/Core/Theme/RegistryLegacyTest.php

@@ -83,7 +83,7 @@ protected function setUp() {
   /**
    * Tests getting legacy theme function registry data defined by a module.
    *
-   * @expectedDeprecation Theme functions are deprecated in drupal:8.0.0 and are removed from drupal:10.0.0. Use Twig templates instead of theme_theme_test(). See https://www.drupal.org/node/1831138
+   * @expectedDeprecation Unsilenced deprecation: Theme functions are deprecated in drupal:8.0.0 and are removed from drupal:10.0.0. Use Twig templates instead of theme_theme_test(). See https://www.drupal.org/node/1831138
    */
   public function testGetLegacyThemeFunctionRegistryForModule() {
     $test_theme = new ActiveTheme([