diff --git a/tools/tests/experiment.py b/tools/tests/experiment.py
index f97a5b14e2..6591ad7d8a 100644
--- a/tools/tests/experiment.py
+++ b/tools/tests/experiment.py
@@ -157,10 +157,14 @@ def force_run(self):
             self.has_run = True
         except sp.CalledProcessError as e:
             ret = e.returncode
-            print(e.output, file=sys.stderr)
+            output = e.output
         finally:
             os.chdir(saved_path)
 
+        output = output.decode('utf-8')
+        if ret:
+            print(output, file=sys.stderr)
+
         return ret
 
     def parse_available_diags(self, packed=True):