<plugin>
        <artifactId>maven-compiler-plugin</artifactId>
        <configuration>
          <excludes>
            <!-- Yes, we want to exclude ForceGuavaCompilation 4 times: -->
            <!-- (And we might as well exclude DummyJavadocClass 3 times (though it would be harmless to include).) -->
            <!-- 1. Don't compile it (since that requires a *non-test* dep on gwt-user. -->

   |
   | It works like this: a POM may declare a repository to use in resolving certain artifacts.
   | However, this repository may have problems with heavy traffic at times, so people have mirrored
   | it to several places.
   |
   | That repository definition will have a unique id, so we can create a mirror reference for that