Bug Report about "rosdep"

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ROS: Indigo OS : Ubuntu14.04

When I run rosdep install turtlesim, the output is:

ERROR: Rosdep experienced an error: XML or text declaration not at start of entity: line 2, column 0
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: 0.11.2

Traceback (most recent call last):
  File "/usr/lib/python2.7/dist-packages/rosdep2/main.py", line 136, in rosdep_main
    exit_code = _rosdep_main(args)
  File "/usr/lib/python2.7/dist-packages/rosdep2/main.py", line 345, in _rosdep_main
    return _package_args_handler(command, parser, options, args)
  File "/usr/lib/python2.7/dist-packages/rosdep2/main.py", line 401, in _package_args_handler
    val = rospkg.expand_to_packages(args, rospack, rosstack)
  File "/usr/lib/python2.7/dist-packages/rospkg/rospack.py", line 428, in expand_to_packages
    package_list = rospack.list()
  File "/usr/lib/python2.7/dist-packages/rospkg/rospack.py", line 188, in list
    self._update_location_cache()
  File "/usr/lib/python2.7/dist-packages/rospkg/rospack.py", line 180, in _update_location_cache
    list_by_path(self._manifest_name, path, cache)
  File "/usr/lib/python2.7/dist-packages/rospkg/rospack.py", line 67, in list_by_path
    root = ElementTree(None, os.path.join(d, PACKAGE_FILE))
  File "/usr/lib/python2.7/xml/etree/ElementTree.py", line 611, in __init__
    self.parse(file)
  File "<string>", line 38, in parse
ParseError: XML or text declaration not at start of entity: line 2, column 0

please help! thanks.