MDL-69078 questions: check for UTF-8 encoding of the import file

Signed-off-by: Daniel Ziegenberg <[email protected]>

question/format/xml/format.php

@@ -58,6 +58,18 @@ class qformat_xml extends qformat_default {
         return 'application/xml';
     }
 
+    /**
+     * Validate the given file.
+     *
+     * For more expensive or detailed integrity checks.
+     *
+     * @param stored_file $file the file to check
+     * @return string the error message that occurred while validating the given file
+     */
+    public function validate_file(stored_file $file): string {
+        return $this->validate_is_utf8_file($file);
+    }
+
     // IMPORT FUNCTIONS START HERE.
 
     /**