(Lowering priority as the problem has been worked around.)

We've got a few options:

1. keep duplicating hacks between submodules and the main docs
2. for each submodule: provide an importable "docs/extra_conf.py" file, and collect those in the main documentation config
3. add autodoc_mock_imports = ['django'] to the documentation config template to work around the current instance of this problem

1. is what we do now; 2. is the most generic solution but adds a bunch of scaffolding to the main docs repository; 3. punts the problem until the next thing we won't be able to import