Switch from using SortedDict to OrderedDict everywhere.
Review Request #10211 — Created Oct. 9, 2018 and submitted
Python 2.7 introduced
OrderedDict, which newer code has been making
use of, but older code written for earlier versions of Python were
instead using Django's
SortedDict. Newer versions of Django don't ship
with this class anymore, and there's no point in using it anyway. This
change moves the few remaining uses over to
Unit tests pass.