iter(dict) is equivalent to iter(dict.keys()). Can simply act on the
dict instead. Provides a more concise, Pythonic syntax and avoids an
unnecessary function call.
Inspired by Lennart Regebro's presentation "Prehistoric Patterns in
Python" at PyCon 2017. Available at:
https://www.youtube.com/watch?v=V5-JH23Vk0I
Subclass django.test.utils.override_settings for similar pattern
Allow use as both TestCase decorator and context manager
Support Django versions 1.4 to 1.8