Every time I start Picard, it warns me that "Plugin directory '…/python2.7/site-packages/contrib/plugins' doesn't exist". But the directory isn't meant to exist anymore, at least on Linux.

It is triggered by tagger.py's line 199 (`self.pluginmanager.load_plugindir(os.path.join(mydir, os.pardir, "contrib", "plugins"))`). It looks like maybe the Windows packaging script is moving files into this directory, so it is maybe still used for Windows Picard? Is it used for OS X? Can it be wrapped in a "are-we-on-Windows" check?