The bash completion installed by app-portage/udept doesn't work for files/directories with spaces.
See Bug 417717 for more details.
The package is dead and masked and there was a big uproar from the user community when I went to last rite it in 2009. Unfortunately, there still is not a suitable replacement and it still works for some things. Here is the package.mask entry:
# Paul Varner <firstname.lastname@example.org> (06 Apr 2009)
# Dead upstream and has issues with newer portages.
# Due to popular demand and no suitable replacement, it will stay in the tree
# in a masked status until it completely breaks or is replaced.