I believe this change has broken things for us for environments that use bundler environment variables:
https://github.com/rails/spring/pull/661/files#diff-badda36a241454b100b8aba52c978271cff008a57451d78e600fa62c3d65d8d9L96-R96

For example, if you set the BUNDLE_PATH=some/path/to/bundle environment variable, it's not picked up because of the Bundler.with_unbundled_env change.