c.g.c.base.testModule transitively pulls in .java files from both modules while reading
            the module description of only the prod module. And the prod module doesn't inherit all
            the modules that the test module classes use, so we get errors.

            The good news is that, despite ignoring errors here, GWT does fail if any errors affect

    while (true) {
      Waiter pred = null;
      Waiter curr = waiters;
      if (curr == Waiter.TOMBSTONE) {
        return; // give up if someone is calling complete
      }
      Waiter succ;
      while (curr != null) {
        succ = curr.next;
        if (curr.thread != null) { // we aren't unlinking this node, update pred.
          pred = curr;