The do_not_use_environment lint tries to catch compile-time use of environment variables, that should be runtime uses.
The message, though, is entirely unclear about this. It just says:

Invalid use of a declared variable

For example, here is some code that triggers this lint:

const bool usingAppEngine = bool.hasEnvironment('APPENGINE_RUNTIME');

Also while I'm at it I should observe that the documentation (https://dart-lang.github.io/linter/lints/do_not_use_environment.html) does not give a "GOOD" code snippet.