presto-main/src/main/java/io/prestosql/server/PluginManager.java/PluginManager/loadPlugin
class PluginManager:    private void loadPlugin(String plugin)
            throws Exception
    {
        log.info("-- Loading plugin %s --", plugin);
        PluginClassLoader pluginClassLoader = buildClassLoader(plugin);
        try (ThreadContextClassLoader ignored = new ThreadContextClassLoader(pluginClassLoader)) {
            loadPlugin(pluginClassLoader);
        }
        log.info("-- Finished loading plugin %s --", plugin);
    }