Comment 7 for bug 1580728

I thought about fixing this with using six.text_type here:

https://github.com/openstack/oslo.versionedobjects/blob/7f0edcdb6430f5ccfdeed81806ecc780753da4d1/oslo_versionedobjects/base.py#L314

But I couldn't get a unit test to work that would recreate the failure, which makes me wonder if it's somehow related to how the logging module handles the formatting.