How to see where rviz is looking for plugins

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I am trying to build a package that add a simple plugins to rviz, following the rviz_plugin_tutorial example. It now compiles with catkin_make. I have the export tag in package.xml and a plugin_description.xml. I have properly source my catkin_workspace.

But if I run rviz, it does not appear in the add panel list. and I have no debug/error anywhere

I am now looking for some ways to debug this. Is there a way to see where 'pluginlib' is looking for plugins, or other way to have a bit more verbosity on the plugin part ?