I guess my posts where a bit confusing, I'll try again:
I want to write a plugin for my ebookreader (PB302), so I can use calibre to copy ebooks to my reader.
I used one of
those as start and changed it.
Then I zipped it and tried to install it. With the gui I get no feedback. Using the command-line (calibre-customize), I get the error message shown above.
Then I copied the file to the folder, where all the built-in plugins are and added it in the calibre/customize/builtin.py. Now it works but I'm wondering if that is the prefered way to do this.
My next step is to change the way the directories are created on the reader. But maybe it is really better to discuss this in another thread.