modprobe: Update error message when path is missing

modprobe: Update error message when path is missing

Currently, modprobe fails with no output by default if the
search paths it tries are missing:

$ modprobe -S notakernel dm-crypt
$
$ modprobe -S notakernel lkjjweiojo
$

This is fairly cryptic and not at all obvious there is a problem
unless the error code is checked or verbose flags are used.
Update the error message to indicate a problem and print out the
directory that failed.