I'm with problems in steps 4 and 5, the tutorial Overlays.

edit

In steps 4 and 5, I can not execute the commands of their. http://www.ros.org/wiki/fuerte/Installation/Overlays

The following erros are shown:

iohan@iohan-HP-Compaq-8200-Elite-SFF-PC:~$ roslocate info turtlebot | rosws merge -
Traceback (most recent call last):
  File "/usr/bin/rosws", line 64, in <module>
    sys.exit(rosinstall.rosws_cli.rosws_main(sys.argv))
  File "/usr/lib/pymodules/python2.7/rosinstall/rosws_cli.py", line 551, in rosws_main
    return ws_commands[command](workspace, args)
  File "/usr/lib/pymodules/python2.7/rosinstall/rosws_cli.py", line 259, in cmd_merge
    config=config)
  File "/usr/lib/pymodules/python2.7/rosinstall/multiproject_cli.py", line 612, in prompt_merge
    extra_verbose))
  File "/usr/lib/pymodules/python2.7/rosinstall/multiproject_cli.py", line 512, in _get_element_diff
    diff = string_diff(old_val, new_val)
  File "/usr/lib/pymodules/python2.7/rosinstall/common.py", line 139, in string_diff
    str1 = str1.ljust(len(str2))
AttributeError: 'list' object has no attribute 'ljust'

the previous steps were executed successfully.