Customer is running docker ./gradlew build on a linux environment and have proxy setup to go to the internet. Its trying to download the dependencies but cannot.
Instructions below should get the user that doesn't have access to the site working if they can download it from another machine and copy it over.
From gradle-wrapper documentation
If you don't want any download to happen when your project is build via gradlew, simply add the Gradle distribution zip to your version control at the location specified by your wrapper configuration. A relative URL is supported - you can specify a distribution file relative to the location of gradle-wrapper.properties file.
So, I changed distributionUrl property in gradle-wrapper.properties to
Make a copy of gradle-2.3-bin.zip in gradle/wrapper/.
build downloaded local copy of zip and built the project.