make check fails with missing translations

[hugobuddel]

make check errors out with

srcdir=. intltool-update -m
The following files contain translations and are currently not in use. Please
consider adding these to the POTFILES.in file, located in the po/ directory.

data/lxpolkit.desktop.in
lxpolkit/main.c
lxsession/app.c

If some of these files are left out on purpose then please add them to
POTFILES.skip instead of POTFILES.in. A file 'missing' containing this list
of left out files has been written in the current directory.
Please report to 
if [ -r missing -o -r notexist ]; then \
  exit 1; \
fi
make[1]: *** [Makefile:165: check] Error 1

These three files are in .gitignore, so I suppose they can be added to POTFILES.skip.

POTFILES.skip contains some similar entries already:

# Autogenerated files with translatable strings.
lxsession-default-apps/main.c
lxsession-default-apps/combobox.c
# This is a source file for configure, output will be translated instead.
data/lxpolkit.desktop.in.in
# bug of intltool with automake 1.15
sub/data/lxpolkit.desktop.in