>>> from keystone import exception
>>> e = exception.Error('what?')
>>> import six
>>> six.text_type(e)
u'what?'
>>> type(e)
<class 'keystone.exception.Error'>
>>> type(six.text_type(e))
<type 'unicode'>
>>> import logging
>>> logging.exception(six.text_type(e))
ERROR:root:what?
None