When attempting to import an extension using the dependency option, an /sce/*.sce.dep is created as soon as the dependency(s) are selected, even if the package already exists in the selected dependency SCE(s) and this message is received:
WARNING: mupdf already exists in below dependency SCE(s), exiting..
bootlist
In above example, mupdf never gets imported as it's already in bootlist.sce, but an orphaned mupdf.sce.dep file gets left in the sce/ directory.