Shopify will need to be fixed to not send an invalid XML element name. E.g. the element name could be prefixed with an underscore. I'll update here when that is done.
The lack of JSON support in the shopify python API is actually caused by the lack of support in pyactiveresource. I have sent JSON support patches upstream to activeresource which you could use. They seem to have been ignored due to lack of upstream activity.
UPDATE: Shopify has been fixed to not return XML with invalid element names. Instead it will prefix an invalid start character with an underscore in the element name.