coleifer/peewee — pull request #477 by jturmel (2014-12-11 07:14:54+00:00)
Title: Fix error when aggregating results that JOIN many-to-many tables

Composite key is a list of primary keys in how the pk_value was being generated causing a crash when trying to be used as a dictionary key since a list isn't hashable.

Now it looks to see if it's a list, if it is, it casts the values to strings and concatenates them together with a dash.