Since its introduction a little over two years ago, the “new” Twisted plugin system has had a minor bug which manifest whenever two or more separate copies of a plugin packaged were available (ie, in sys.path). Normally, the first of these should obscure the second. However, the plugin system would allow both to be discovered. This could lead to confusing results in some cases.
This bug is now fixed in trunk@HEAD: only the first plugin package on sys.path will be considered for plugins. Plugin directories (not packages) will still be considered.