Error Invalid <param> tag on running roscore

edit

I'm getting the following output when I run roscore:

WARNING: unable to configure logging. No log files will be generated
Checking log directory for disk usage. This may take awhile.
Press Ctrl-C to interrupt
Done checking log file disk usage. Usage is <1GB.

Traceback (most recent call last):
  File "/usr/bin/rosversion", line 9, in <module>
    load_entry_point('rospkg==1.1.7', 'console_scripts', 'rosversion')()
  File "/usr/lib/python2.7/dist-packages/rospkg/rosversion.py", line 106, in main
    version = rosstack.get_stack_version(args.package)
  File "/usr/lib/python2.7/dist-packages/rospkg/rospack.py", line 422, in get_stack_version
    return get_stack_version_by_dir(self.get_path(stack))
  File "/usr/lib/python2.7/dist-packages/rospkg/rospack.py", line 201, in get_path
    self._update_location_cache()
  File "/usr/lib/python2.7/dist-packages/rospkg/rospack.py", line 184, 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
cElementTree.ParseError: XML or text declaration not at start of entity: line 1, column 1
Invalid <param> tag: Cannot load command parameter [rosversion]: command [rosversion roslaunch] returned with code [1]. 

Param xml is <param command="rosversion roslaunch" name="rosversion"/>
The traceback for the exception was written to the log file

I've seen my issue is related to.
There they point out that I might have both pip and a debianpython installed and the shouls keep the debian only. Once Ubuntu relays on python I'm afraid of delete wrong files and mess up my system. My question is: is that correct? Can I delete pip python?

EDIT #1: add rosversion roslaunch log

     Traceback (most recent call last):
  File "/usr/bin/rosversion", line 9, in <module>
    load_entry_point('rospkg==1.1.7', 'console_scripts', 'rosversion')()
  File "/usr/lib/python2.7/dist-packages/rospkg/rosversion.py", line 106, in main
    version = rosstack.get_stack_version(args.package)
  File "/usr/lib/python2.7/dist-packages/rospkg/rospack.py", line 422, in get_stack_version
    return get_stack_version_by_dir(self.get_path(stack))
  File "/usr/lib/python2.7/dist-packages/rospkg/rospack.py", line 201, in get_path
    self._update_location_cache()
  File "/usr/lib/python2.7/dist-packages/rospkg/rospack.py", line 184, 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
cElementTree.ParseError: XML or text declaration not at start of entity: line 1, column 1