bug

bug

```
Traceback (most recent call last):
  File "src/gevent/greenlet.py", line 716, in gevent._greenlet.Greenlet.run
  File "/home/cosmin/Documents/WORK/GITHUB/raiden/raiden/network/transport/matrix.py", line 733, in _handle_presence_change
    address = self._validate_userid_signature(user)
  File "/home/cosmin/.virtualenvs/raiden/lib/python3.6/site-packages/cachetools/__init__.py", line 87, in wrapper
    v = method(self, *args, **kwargs)
  File "/home/cosmin/Documents/WORK/GITHUB/raiden/raiden/network/transport/matrix.py", line 874, in _validate_userid_signature
    displayname = user.get_display_name()
  File "/home/cosmin/.virtualenvs/raiden/lib/python3.6/site-packages/matrix_client/user.py", line 36, in get_display_name
    self.displayname = self.api.get_display_name(self.user_id)
  File "/home/cosmin/.virtualenvs/raiden/lib/python3.6/site-packages/matrix_client/api.py", line 705, in get_display_name
    content = self._send("GET", "/profile/%s/displayname" % user_id)
  File "/home/cosmin/.virtualenvs/raiden/lib/python3.6/site-packages/raiden_libs/network/matrix/client.py", line 72, in _send
    return super()._send(method, path, *args, **kwargs)
  File "/home/cosmin/.virtualenvs/raiden/lib/python3.6/site-packages/matrix_client/api.py", line 681, in _send
    errordata = json.loads(response.json()['error'])
  File "/usr/lib/python3.6/json/__init__.py", line 354, in loads
    return _default_decoder.decode(s)
  File "/usr/lib/python3.6/json/decoder.py", line 339, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/lib/python3.6/json/decoder.py", line 357, in raw_decode
    raise JSONDecodeError("Expecting value", s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)
2018-08-23T10:19:01Z <Greenlet "Greenlet-0" at 0x7f7a0e64b948: <bound method MatrixTransport._handle_presence_change of <raiden.network.transport.matrix.MatrixTransport object at 0x7f7a0f7a3cc0>>({'content': {'currently_active': True, 'last_activ)> failed with JSONDecodeError

Traceback (most recent call last):
  File "/home/cosmin/.virtualenvs/raiden/bin/raiden", line 11, in <module>
    load_entry_point('raiden', 'console_scripts', 'raiden')()
  File "/home/cosmin/Documents/WORK/GITHUB/raiden/raiden/__main__.py", line 11, in main
    run(auto_envvar_prefix='RAIDEN')  # pylint: disable=no-value-for-parameter
  File "/home/cosmin/.virtualenvs/raiden/lib/python3.6/site-packages/click/core.py", line 722, in __call__
    return self.main(*args, **kwargs)
  File "/home/cosmin/.virtualenvs/raiden/lib/python3.6/site-packages/click/core.py", line 697, in main
    rv = self.invoke(ctx)
  File "/home/cosmin/.virtualenvs/raiden/lib/python3.6/site-packages/click/core.py", line 1043, in invoke
    return Command.invoke(self, ctx)
  File "/home/cosmin/.virtualenvs/raiden/lib/python3.6/site-packages/click/core.py", line 895, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/cosmin/.virtualenvs/raiden/lib/python3.6/site-packages/click/core.py", line 535, in invoke
    return callback(*args, **kwargs)
  File "/home/cosmin/.virtualenvs/raiden/lib/python3.6/site-packages/click/decorators.py", line 17, in new_func
    return f(get_current_context(), *args, **kwargs)
  File "/home/cosmin/Documents/WORK/GITHUB/raiden/raiden/ui/cli.py", line 1064, in run
    NodeRunner(kwargs, ctx).run()
  File "/home/cosmin/Documents/WORK/GITHUB/raiden/raiden/ui/cli.py", line 923, in run
    app = self._run_app()
  File "/home/cosmin/Documents/WORK/GITHUB/raiden/raiden/ui/cli.py", line 941, in _run_app
    app_ = run_app(**self._options)
  File "/home/cosmin/Documents/WORK/GITHUB/raiden/raiden/ui/cli.py", line 765, in run_app
    raiden_app.start()
  File "/home/cosmin/Documents/WORK/GITHUB/raiden/raiden/app.py", line 132, in start
    self.raiden.start()
  File "/home/cosmin/Documents/WORK/GITHUB/raiden/raiden/raiden_service.py", line 310, in start
    self.start_async().wait()
  File "/home/cosmin/Documents/WORK/GITHUB/raiden/raiden/raiden_service.py", line 293, in start_async
    self.transport.start(self, queueids_to_queues)
  File "/home/cosmin/Documents/WORK/GITHUB/raiden/raiden/network/transport/matrix.py", line 197, in start
    self._join_discovery_room()
  File "/home/cosmin/Documents/WORK/GITHUB/raiden/raiden/network/transport/matrix.py", line 361, in _join_discovery_room
    discovery_room = self._client.join_room(discovery_room_alias_full)
  File "/home/cosmin/.virtualenvs/raiden/lib/python3.6/site-packages/matrix_client/client.py", line 320, in join_room
    response = self.api.join_room(room_id_or_alias)
  File "/home/cosmin/.virtualenvs/raiden/lib/python3.6/site-packages/matrix_client/api.py", line 195, in join_room
    return self._send("POST", path)
  File "/home/cosmin/.virtualenvs/raiden/lib/python3.6/site-packages/raiden_libs/network/matrix/client.py", line 72, in _send
    return super()._send(method, path, *args, **kwargs)
  File "/home/cosmin/.virtualenvs/raiden/lib/python3.6/site-packages/matrix_client/api.py", line 681, in _send
    errordata = json.loads(response.json()['error'])
  File "/usr/lib/python3.6/json/__init__.py", line 354, in loads
    return _default_decoder.decode(s)
  File "/usr/lib/python3.6/json/decoder.py", line 339, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
  File "/usr/lib/python3.6/json/decoder.py", line 357, in raw_decode
    raise JSONDecodeError("Expecting value", s, err.value) from None
json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)
```