Leapp upgrade fails to handle non UTF-8 characters gracefully

Issue

• leapp upgrade is giving below traceback error,

  Traceback (most recent call last):
  File "/usr/lib64/python2.7/multiprocessing/process.py", line 258, in _bootstrap
  self.run()
  File "/usr/lib64/python2.7/multiprocessing/process.py", line 114, in run
  self._target(*self._args, **self._kwargs)
  File "/usr/lib/python2.7/site-packages/leapp/repository/actor_definition.py", line 72, in _do_run
  actor_instance.run(*args, **kwargs)
  File "/usr/lib/python2.7/site-packages/leapp/actors/__init__.py", line 335, in run
  self.process(*args)
  File "/usr/share/leapp-repository/repositories/system_upgrade/el7toel8/actors/rootscanner/actor.py", line 27, in process
  self.produce(RootDirectory(items=subdirs))
  File "/usr/lib/python2.7/site-packages/leapp/actors/__init__.py", line 359, in produce
  self._messaging.produce(model, self)
  File "/usr/lib/python2.7/site-packages/leapp/messaging/__init__.py", line 196, in produce
  return self._do_produce(model, actor, self._new_data)
  File "/usr/lib/python2.7/site-packages/leapp/messaging/__init__.py", line 214, in _do_produce
  data = json.dumps(model.dump(), sort_keys=True)
  File "/usr/lib64/python2.7/json/__init__.py", line 250, in dumps
  sort_keys=sort_keys, **kw).encode(obj)
  File "/usr/lib64/python2.7/json/encoder.py", line 209, in encode
  chunks = list(chunks)
  File "/usr/lib64/python2.7/json/encoder.py", line 434, in _iterencode
  for chunk in _iterencode_dict(o, _current_indent_level):
  File "/usr/lib64/python2.7/json/encoder.py", line 408, in _iterencode_dict
  for chunk in chunks:
  File "/usr/lib64/python2.7/json/encoder.py", line 332, in _iterencode_list
  for chunk in chunks:
  File "/usr/lib64/python2.7/json/encoder.py", line 390, in _iterencode_dict
  yield _encoder(value)
  UnicodeDecodeError: 'utf8' codec can't decode byte 0xc0 in position 0: invalid start byte