catch if package is not found / do not download the data if the target directory is not writeable

[k-okada]

Somehow the empty directory is not copied to the release repository, and I think it's ok to not to include sample/trained data into deb package as for now...

https://github.com/jsk-ros-pkg/jsk_recognition/tree/master/jsk_perception/sample/data
https://github.com/tork-a/jsk_recognition-release/tree/debian/indigo/trusty/jsk_perception/data

Current error message is something like this, and if we do not install jsk_perception,

make[4]: Leaving directory `/tmp/jsk_recognition-release/obj-x86_64-linux-gnu'
make -f CMakeFiles/install_sample_data.dir/build.make CMakeFiles/install_sample_data.dir/build
make[4]: Entering directory `/tmp/jsk_recognition-release/obj-x86_64-linux-gnu'
../scripts/install_sample_data.py
Checking md5sum of '/home/k-okada/.ros/data/2016-06-10-23-01-28_in_lab.bag'...
...done
Traceback (most recent call last):
  File "../scripts/install_sample_data.py", line 22, in <module>
    main()
  File "../scripts/install_sample_data.py", line 16, in main
    'sample/data/2016-06-10-23-01-28_in_lab.bag',
  File "/opt/ros/indigo/lib/python2.7/dist-packages/jsk_data/download_data.py", line 103, in download_data
    os.makedirs(osp.dirname(path))
  File "/usr/lib/python2.7/os.py", line 157, in makedirs
    mkdir(name, mode)
OSError: [Errno 13] Permission denied: '/opt/ros/indigo/share/jsk_perception/sample/data'
make[4]: *** [CMakeFiles/install_sample_data] Error 1

we'll get

../scripts/install_sample_data.py
Traceback (most recent call last):
  File "../scripts/install_sample_data.py", line 22, in <module>
    main()
  File "../scripts/install_sample_data.py", line 16, in main
    'sample/data/2016-06-10-23-01-28_in_lab.bag',
  File "/opt/ros/indigo/lib/python2.7/dist-packages/jsk_data/download_data.py", line 84, in download_data
    pkg_path = rp.get_path(pkg_name)
  File "/usr/lib/python2.7/dist-packages/rospkg/rospack.py", line 200, in get_path
    raise ResourceNotFound(name, ros_paths=self._ros_paths)
rospkg.common.ResourceNotFound: jsk_perception
ROS path [0]=/opt/ros/indigo/share/ros
ROS path [1]=/opt/ros/indigo/share
ROS path [2]=/opt/ros/indigo/stacks