fix TypeError under osx & py3k

[benureau]

Got this error under OSX 10.11.4 with Python 3.5.1:

$ rosdep install --from-paths src --ignore-src --rosdistro jade -y --as-root pip:no --skip-keys=gazebo

ERROR: Rosdep experienced an error: a bytes-like object is required, not 'str'
Please go to the rosdep page [1] and file a bug report with the stack trace below.
[1] : http://www.ros.org/wiki/rosdep

rosdep version: 0.11.4

Traceback (most recent call last):
  File "/Users/fabien/.pyenv/versions/3.5.1/lib/python3.5/site-packages/rosdep-0.11.4-py3.5.egg/rosdep2/main.py", line 136, in rosdep_main
    exit_code = _rosdep_main(args)
  File "/Users/fabien/.pyenv/versions/3.5.1/lib/python3.5/site-packages/rosdep-0.11.4-py3.5.egg/rosdep2/main.py", line 353, in _rosdep_main
    return _package_args_handler(command, parser, options, args)
  File "/Users/fabien/.pyenv/versions/3.5.1/lib/python3.5/site-packages/rosdep-0.11.4-py3.5.egg/rosdep2/main.py", line 447, in _package_args_handler
    return command_handlers[command](lookup, packages, options)
  File "/Users/fabien/.pyenv/versions/3.5.1/lib/python3.5/site-packages/rosdep-0.11.4-py3.5.egg/rosdep2/main.py", line 654, in command_install
    installer.install(uninstalled, **install_options)
  File "/Users/fabien/.pyenv/versions/3.5.1/lib/python3.5/site-packages/rosdep-0.11.4-py3.5.egg/rosdep2/installers.py", line 485, in install
    verbose=verbose, quiet=quiet)
  File "/Users/fabien/.pyenv/versions/3.5.1/lib/python3.5/site-packages/rosdep-0.11.4-py3.5.egg/rosdep2/installers.py", line 515, in install_resolved
    command = installer.get_install_command(resolved, interactive=interactive, reinstall=reinstall, quiet=quiet)
  File "/Users/fabien/.pyenv/versions/3.5.1/lib/python3.5/site-packages/rosdep-0.11.4-py3.5.egg/rosdep2/platforms/osx.py", line 316, in get_install_command
    resolved = self.remove_duplicate_dependencies(resolved)
  File "/Users/fabien/.pyenv/versions/3.5.1/lib/python3.5/site-packages/rosdep-0.11.4-py3.5.egg/rosdep2/platforms/osx.py", line 347, in remove_duplicate_dependencies
    if brew_strip_pkg_name(other.package) == brew_strip_pkg_name(d):
  File "/Users/fabien/.pyenv/versions/3.5.1/lib/python3.5/site-packages/rosdep-0.11.4-py3.5.egg/rosdep2/platforms/osx.py", line 157, in brew_strip_pkg_name
    return package.split('/')[-1]
TypeError: a bytes-like object is required, not 'str

This is due to package sometimes being of type bytes. This is fixed by this pull request. I did not test it under any other version than Python 3.5.1.

[wjwwood]

lgtm, thanks