Convert warning to RuntimeException.

Closes #3440038

core/modules/image/src/Plugin/Field/FieldType/ImageItem.php

@@ -9,6 +9,7 @@
 use Drupal\Core\File\Exception\FileException;
 use Drupal\Core\File\FileSystemInterface;
 use Drupal\Core\Form\FormStateInterface;
+use Drupal\Core\Logger\LoggerChannelTrait;
 use Drupal\Core\StreamWrapper\StreamWrapperInterface;
 use Drupal\Core\StringTranslation\TranslatableMarkup;
 use Drupal\Core\TypedData\DataDefinition;
@@ -52,6 +53,8 @@
  */
 class ImageItem extends FileItem {
 
+  use LoggerChannelTrait;
+
   /**
    * {@inheritdoc}
    */
@@ -332,7 +335,7 @@ public function preSave() {
       }
     }
     else {
-      trigger_error(sprintf("Missing file with ID %s.", $this->target_id), E_USER_WARNING);
+      $this->getLogger('image')->warning("Missing file with ID %id.", ['%id' => $this->target_id]);
     }
   }