result.stdout might contain character which can't be decoded with 'ascii',

use utf-8 instead

Author: tomasstupka

graalpython/com.oracle.graal.python.test/src/tests/test_tagged_unittests.py

@@ -108,7 +108,7 @@ def run_serialize_out(cmd):
         if append_out:
             message += LINE + "\n"
             message += "output:\n"
-            message += result.stdout.decode('ascii')
+            message += result.stdout.decode('utf-8')
             message += LINE + "\n"
         print(message)
         if result.returncode: