Just curious if this is bug ticket worthy. In config files, I can use the interpolation like

%(<http://env.MY|env.MY>_ENV_VAR)s

successfully. I wanted to provide a default if it wasn't set and do something like

%(<http://env.MY|env.MY>_ENV_VAR=none)s

. This is valid syntax and it seems to parse and work fine, but it doesn't respect the environment variables set when this happens. I've only tested this on 2.24.0.