I've never had an issue with things in the folder "assets" under src. For some reason, it cannot understand a "locale" directory.
Not an issue to copy the folder in bin-debug then do a build.
If this is the only work around, for a release build, you have to start the wizard and then cancel out of it, so the bin-release directory is created. Copy the locale folder into the bin-release folder, then open the release wizard and you will now see the locale directory in the packages. Successful completion of a release, remove the bin-release directory.