just an explanatory motivation on this (and everything similar suck as this):  common environments have default, base settings;  they are overridden by a heirarchy of environment settings.   For example, following https://github.com/edx/edx-platform/wiki/Internationalization-and-localization,  you might have cms/envs/devstack_something.py override (and include)  devstack.py, which in turn might import aws.py, which in turn imports common.py.   Hope this is helpful.