All data having to do with HTTP requests and responses is generally a byte string and now marked as such. See https://docs.djangoproject.com/en/dev/topics/python3/#httprequest-and-httpresponse-objects Classes with a __unicode__ representation have been updated to use the python_2_compatible_unicode decorator.
This now imitates the tox test suite.
Product.stockrecord was a deprecated helper to get the first stockrecord for a product, so it was potentially the wrong stockrecord to look at anyway. Using the price stored on the basket line is the correct thing to do, and avoids the AttributeError as Product.stockrecord has since been removed.