Environment-specific settings for python 2 modules

A little trick we came up with for a recent project. When developing back-end software in python or any other language there is often a need to load different values for configuration settings based on environment. A typical case is a database connection address and port, for example, that would be different when working locally vs. test vs. production. There are lots of ways to do this, but this one worked well for us. The technique relies on setting an environment variable with the name of the environment, and then using that name to load a default settings file and an environment-specific settings file and merge them both into the global namespace.