roscore is showing error of keyboard interruptions and errors in file os.py .i have reinstalled it twice but not getting the results .

edit

 youbot@youbot-HP-450-Notebook-PC:~$ roscore
... logging to /home/youbot/.ros/log/003be028-4fda-11e5-bd82-74e543a474c0/roslaunch-youbot-HP-450-Notebook-PC-18427.log
Checking log directory for disk usage. This may take awhile.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

started roslaunch server http://youbot-HP-450-Notebook-PC:34366/
ros_comm version 1.8.11


SUMMARY
========

PARAMETERS
 * /rosdistro
 * /rosversion

NODES

auto-starting new master
process[master]: started with pid [18447]
ERROR: could not contact master [http://youbot-HP-450-Notebook-PC:11311/]
[master] killing on exit
Traceback (most recent call last):
  File "/opt/ros/fuerte/bin/rosmaster", line 35, in <module>
    rosmaster.rosmaster_main()
  File "/opt/ros/fuerte/lib/python2.7/dist-packages/rosmaster/main.py", line 73, in rosmaster_main
    configure_logging()   
  File "/opt/ros/fuerte/lib/python2.7/dist-packages/rosmaster/main.py", line 57, in configure_logging
    _log_filename = rosgraph.roslogging.configure_logging('rosmaster', logging.DEBUG, filename=filename)
  File "/opt/ros/fuerte/lib/python2.7/dist-packages/rosgraph/roslogging.py", line 86, in configure_logging
    rosgraph_d = rospkg.RosPack().get_path('rosgraph')
  File "/usr/local/lib/python2.7/dist-packages/rospkg/rospack.py", line 197, in get_path
    self._update_location_cache()
  File "/usr/local/lib/python2.7/dist-packages/rospkg/rospack.py", line 180, in _update_location_cache
    list_by_path(self._manifest_name, path, cache)
  File "/usr/local/lib/python2.7/dist-packages/rospkg/rospack.py", line 61, in list_by_path
    for d, dirs, files in os.walk(path, topdown=True, followlinks=True):
  File "/usr/lib/python2.7/os.py", line 294, in walk
    for x in walk(new_path, topdown, onerror, followlinks):
  File "/usr/lib/python2.7/os.py", line 294, in walk
    for x in walk(new_path, topdown, onerror, followlinks):
  File "/usr/lib/python2.7/os.py", line 294, in walk
    for x in walk(new_path, topdown, onerror, followlinks):
  File "/usr/lib/python2.7/os.py", line 294, in walk
    for x in walk(new_path, topdown, onerror, followlinks):
  File "/usr/lib/python2.7/os.py", line 294, in walk
    for x in walk(new_path, topdown, onerror, followlinks):
  File "/usr/lib/python2.7/os.py", line 294, in walk
    for x in walk(new_path, topdown, onerror, followlinks):
  File "/usr/lib/python2.7/os.py", line 294, in walk
    for x in walk(new_path, topdown, onerror, followlinks):
  File "/usr/lib/python2.7/os.py", line 294, in walk
    for x in walk(new_path, topdown, onerror, followlinks):
  File "/usr/lib/python2.7/os.py", line 294, in walk
    for x in walk(new_path, topdown, onerror, followlinks):
  File "/usr/lib/python2.7/os.py", line 294, in walk
    for x in walk(new_path, topdown, onerror, followlinks):
  File "/usr/lib/python2.7/os.py", line 294, in walk
    for x in walk(new_path, topdown, onerror, followlinks):
  File "/usr/lib/python2.7/os.py", line 294, in walk
    for x in walk(new_path, topdown, onerror, followlinks):
  File "/usr/lib/python2.7/os.py", line 294, in walk
    for x in walk(new_path, topdown, onerror, followlinks):
  File "/usr/lib/python2.7/os.py", line 294, in walk
    for x in walk(new_path, topdown, onerror, followlinks):
  File "/usr/lib/python2.7/os.py", line 294, in walk
    for x in walk(new_path, topdown, onerror, followlinks):
  File "/usr/lib/python2.7 ...