Do dictionary-order-independent comparison in test_printcat

`test_printcat` was generating a dictionary, and then comparing it to a file on disk.  We were getting lucky that the order wasn't changing around, but on Python 3.4 it definitely does.  This re-evaluates the dictionary from disk and then compares the dictionaries as dictionaries, rather than strings, so the ordering doesn't matter.  Probably worth merging even regardless of Python 3.4.

@pllim