linaro-media-create doesn't check if --hwpack is a real file

[Lee Jones]

For example, if you provide --hwpack ~/dirname/ l-m-c will not provide a valid "--hwpack argument needs to be a regular file".

Instead this is seen:
cp: omitting directory `hwpacks/hwpack.maverick.linaro.bsp-ux500/'
Traceback (most recent call last):
  File "/usr/bin/linaro-media-create", line 122, in <module>
    install_hwpacks(ROOTFS_DIR, TMP_DIR, args.hwpack_force_yes, *hwpacks)
  File "/usr/lib/pymodules/python2.6/linaro_media_create/hwpack.py", line 55, in install_hwpacks
    install_hwpack(chroot_dir, hwpack_file, hwpack_force_yes)
  File "/usr/lib/pymodules/python2.6/linaro_media_create/hwpack.py", line 68, in install_hwpack
    copy_file(hwpack_file, chroot_dir)
  File "/usr/lib/pymodules/python2.6/linaro_media_create/hwpack.py", line 101, in copy_file
    cmd_runner.run(['cp', filepath, directory], as_root=True).wait()
  File "/usr/lib/pymodules/python2.6/linaro_media_create/cmd_runner.py", line 65, in wait
    raise SubcommandNonZeroReturnValue(self._my_args, returncode)
linaro_media_create.cmd_runner.SubcommandNonZeroReturnValue: Sub process "['sudo', 'cp', 'hwpacks/hwpack.maverick.linaro.bsp-ux500/', '/tmp/tmpaGDA58/binary']" returned a non-zero value

[Guilherme Salgado (salgado)]

 status triaged
 priority low