Comment 2 for bug 1130601

Julien commented in IRC that this is likely caused by "the str() of the dict" being encoded. It sounds like our dictionary flattening code, used to produce the value to go in to be signed, isn't handling recursion into data structures other than dictionaries. Early on the metadata was just nested dictionaries with strings as keys and values but apparently we've got a sequence in one of the values now. JSON encodes all sequences as lists, but the sender is actually a tuple in this case so the str() of that value comes out differently.