dbus: Server address of type unix was missing argument path or abstract

When running as root (or with sudo) I get the following traceback
```
# ntfy send 'aa'
ERROR: Failed to send notification using default
Traceback (most recent call last):
File "/root/.local/lib/python3.7/site-packages/ntfy/backends/default.py", line 20, in notify
module.notify(title=title, message=message, **kwargs)
File "/root/.local/lib/python3.7/site-packages/ntfy/backends/linux.py", line 31, in notify
bus = dbus.SessionBus()
File "/usr/lib/python3.7/site-packages/dbus/_dbus.py", line 211, in __new__
mainloop=mainloop)
File "/usr/lib/python3.7/site-packages/dbus/_dbus.py", line 100, in __new__
bus = BusConnection.__new__(subclass, bus_type, mainloop=mainloop)
File "/usr/lib/python3.7/site-packages/dbus/bus.py", line 122, in __new__
bus = cls._new_for_bus(address_or_type, mainloop=mainloop)
dbus.exceptions.DBusException: org.freedesktop.DBus.Error.BadAddress: Server address of type unix was missing argument path or abstract

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
File "/root/.local/lib/python3.7/site-packages/ntfy/__init__.py", line 58, in notify
**backend_config)
File "/root/.local/lib/python3.7/site-packages/ntfy/backends/default.py", line 22, in notify
raise DefaultNotifierError(e, module)
ntfy.backends.default.DefaultNotifierError: (DBusException('Server address of type unix was missing argument path or abstract'), )
```

System: Archlinux x64
```
ntfy --version
2.6.0

local/dbus 1.12.10-2
Freedesktop.org message bus system
local/python-dbus 1.2.8-2
Python bindings for DBUS
```

any ideas?