When using the ProxyConfiguration.open() method to access external resources, it is possible to face a 302. Even if URLConnection.followRedirects is by default set to true, it is possible to have some plugins changing this value (see https://github.com/jenkinsci/kubernetes-pipeline-plugin/pull/31).

In such cases, it would be great to make sure the 302 are followed in the ProxyConfiguration or at least log that it won't be due to the setting.