private void assertUpgradeFails(String from, String to, DeployTester tester, RpcServer rpcServer, String expected) throws IOException {
        Version versionToUpgradeTo = Version.fromString(to);
        VersionState versionState = createVersionState(tester.curator(), versionToUpgradeTo);
        Bootstrapper bootstrap = createBootstrapper(tester, rpcServer, VIP_STATUS_PROGRAMMATICALLY, versionState);
        bootstrap.versionState().storeVersion(from);
        try {
            bootstrap.doStart();
            fail("Expected bootstrap to fail");
        } catch (RuntimeException e) {
            assertEquals(expected, e.getMessage());
        }
    }
@author Ulf Lilleengen
@author Harald Musum
configserver/src/test/java/com/yahoo/vespa/config/server/ConfigServerBootstrapTest.java