generation: Fix bytes/str error

This was probably left over from supporting Python 2 in the scripts.

tools/generation/lib/test.py

@@ -55,7 +55,7 @@ class Test:
             ' * ' + self.file_name,
             ' * ----------------------------------------------------------------',
             ' */',
-            self.source,
+            self.source.decode('utf-8'),
             '\n'])
 
     @after_parse