Index: lnt/testing/profile/profile.py
===================================================================
--- lnt/testing/profile/profile.py
+++ lnt/testing/profile/profile.py
@@ -115,7 +115,7 @@
 
         Implementation note: the string is base64 encoded.
         """
-        return base64.b64encode(self.impl.serialize())
+        return base64.b64encode(self.impl.serialize()).decode('ascii')
 
     def upgrade(self):
         """