Model signatures were storing fields in a standard dictionary, ignoring

the order provided by the model. For actual evolution operations, the

order doesn't matter at all, but this did lead to some model diffing

showing unexpected orders ("field3" before "field2", for instance).
The biggest problem had to do when working toward the Python 3 port. Our

unit tests were working off the dictionary order, which was stable

across Python 2, but changed (twice) in 3. This meant that most unit

tests failed, since the generated order of fields and mutations were

different from what was expected.
We now retain sort orders for fields by storing field information in an

OrderedDict. This lets diffing, mutations, and unit tests all work off

the order shown in the model instead of whatever comes out of dictionary

iteration. That does mean a lot of unit tests had to change, which is

the bulk of the change, but it provides stability across all versions of

Python.

Unit tests pass for all supported versions of Django and all database

types. Tested with Python 2.7 and (with upcoming changes) Python 3.4,

3.5, and 3.6.