commit 03a3be834008f2cb3bd77f29d6dc5c2a7cfb8fef
Author: Ivan Kolodyazhny <e0ne@e0ne.info>
Date:   Mon Oct 12 22:23:00 2020 +0300

    Fix error handling on instance create
    
    exception.BadRequest expects string as a 'message' argument, so we can't
    pass ValueError without casting it to string.
    
    Change-Id: Iff43c38dca596e694cc7c6bc20e71669d83e31e2

diff --git a/trove/instance/service.py b/trove/instance/service.py
index 66c5547..3884f9e 100644
--- a/trove/instance/service.py
+++ b/trove/instance/service.py
@@ -431,7 +431,7 @@ class InstanceController(wsgi.Controller):
             users = populate_users(body['instance'].get('users', []),
                                    database_names)
         except ValueError as ve:
-            raise exception.BadRequest(message=ve)
+            raise exception.BadRequest(message=str(ve))
         if slave_of_id and (databases or users):
             raise exception.ReplicaCreateWithUsersDatabasesError()