Python dbus error on Linux when sending notification

[Dev3XOR]

I use plyer in virtual environment. Whenever I call notification.notify I get a warning:

UserWarning: The Python dbus package is not installed.
Try installing it with your distribution's package manager, it is usually called python-dbus or python3-dbus, but you might have to try dbus-python instead, e.g. when using pip.
  warnings.warn(msg)

I can see notification works though.
Now when I've tried to install dbus-python notifictions refused to work at all and I get this error:

ERROR:dbus.connection:Unable to set arguments ('', 0, None, "Time's Up!", 'Your timer has reached 0', [], [], 20000) according to signature 'susssasa{sv}i': <class 'TypeError'>: Expected a string or unicode object
Exception in thread Thread-60:
Traceback (most recent call last):
  File "~/.pyenv/versions/3.10.0/lib/python3.10/threading.py", line 1009, in _bootstrap_inner
    self.run()
  File "~/.pyenv/versions/3.10.0/lib/python3.10/threading.py", line 1358, in run
    self.function(*self.args, **self.kwargs)
  File "~/Projekty/pomodoro/src/pomodoro/__init__.py", line 40, in func_wrapper
    self.on_ready()
  File "~/Projekty/pomodoro/src/pomodoro/__init__.py", line 139, in clock_ready
    notification.notify(
  File "~/.virtualenvs/pomodoro/lib/python3.10/site-packages/plyer/facades/notification.py", line 79, in notify
    self._notify(
  File "~/.virtualenvs/pomodoro/lib/python3.10/site-packages/plyer/platforms/linux/notification.py", line 46, in _notify
    interface.Notify(
  File "~/.virtualenvs/pomodoro/lib/python3.10/site-packages/dbus/proxies.py", line 72, in __call__
    return self._proxy_method(*args, **keywords)
  File "~/.virtualenvs/pomodoro/lib/python3.10/site-packages/dbus/proxies.py", line 141, in __call__
    return self._connection.call_blocking(self._named_service,
  File "~/.virtualenvs/pomodoro/lib/python3.10/site-packages/dbus/connection.py", line 643, in call_blocking
    message.append(signature=signature, *args)
TypeError: Expected a string or unicode object

The same occures when I try to run program outside of virtualenv (python3-dbus is installed globaly on my machine).

[Dev3XOR]

OK, silly me. Solution was simple. The problem was that app_icon was set to None which works without dbus, but throws error when it's present. Sorry for the mess.