Pretty for doctest

[keitheis]

now for ugly example:
.../serializer/invoice.py .2020-08-10 16:51:19 INFO [<doctest ....serializer.invoice.InvoiceCustomFunctions._func_patch_manual_tag_pricing_adjustment[5]>] [{'uuid': '5e8848cb-812f-9999-8238-c24b1cd28789', 'name': '- 減價', 'price': 0}]