How to debug plugin loading?

[yosefm]

Hello,
I'm trying to create a Designer plugin using PyQt. I have my plugin in ~/prog and the plugin class in ~/prog/plugins.

I tried to run Designer with
PYQTDESIGNERPATH=~/prog/plugins/ PYTHONPATH=~/prog/ designer and couldn't see the plugin loaded.

So, how fo I see what directories are searched, what files are loaded and what errors occur in the process?

Thanks.

[yosefm]

Additional info: I don't think the problem is with my code, since I tried running examples/designer/plugins.py from PyQt4's examples, but that diodn't load any modules too.