I am using the gtk3 branch with python3 on openSUSE Tumbleweed. They upgraded python to python3.7 and this gives me the following when starting nautilus (rabbitvcs still works):

/usr/lib/python3.7/site-packages/rabbitvcs/services/checkerservice.py:60: DeprecationWarning: Importing dbus.glib to use the GLib main loop with dbus-python is deprecated.
Instead, use this sequence:

from dbus.mainloop.glib import DBusGMainLoop

  DBusGMainLoop(set_as_default=True)

import dbus.glib # FIXME: this might actually already set the default loop
/usr/lib/python3.7/site-packages/rabbitvcs/services/checkerservice.py:429: PyGIDeprecationWarning: Since version 3.11, calling threads_init is no longer needed. See: https://wiki.gnome.org/PyGObject/Threading
gobject.threads_init()
/usr/lib/python3.7/site-packages/rabbitvcs/services/checkerservice.py:436: PyGIDeprecationWarning: GObject.MainLoop is deprecated; use GLib.MainLoop instead
mainloop = gobject.MainLoop()
/usr/lib/python3.7/site-packages/rabbitvcs/services/checkerservice.py:440: PyGIDeprecationWarning: GObject.idle_add is deprecated; use GLib.idle_add instead
gobject.idle_add(sys.stdout.write, "Started status checker service\n")
/usr/lib/python3.7/site-packages/rabbitvcs/services/checkerservice.py:441: PyGIDeprecationWarning: GObject.idle_add is deprecated; use GLib.idle_add instead
gobject.idle_add(sys.stdout.flush)

I switched to that branch since master and python2 doesn't work on my system (made previous bugreports about that)