xpra breaks with python3.8 3.8.4~rc1-1

$ firejail --x11 xeyes

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Error during threaded setup of <class 'xpra.server.mixins.child_command_server.ChildCommandServer'>
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/xpra/server/server_base.py", line 170, in threaded_init
    c.threaded_setup(self)
  File "/usr/lib/python3/dist-packages/xpra/server/mixins/child_command_server.py", line 92, in threaded_setup
    load_xdg_menu_data()
  File "/usr/lib/python3/dist-packages/xpra/platform/xposix/xdg_helper.py", line 237, in load_xdg_menu_data
    xdg_menu_data = do_load_xdg_menu_data()
  File "/usr/lib/python3/dist-packages/xpra/platform/xposix/xdg_helper.py", line 268, in do_load_xdg_menu_data
    menu = parse()
  File "/usr/lib/python3/dist-packages/xdg/Menu.py", line 1137, in parse
    return XMLMenuBuilder(debug).parse(filename)
  File "/usr/lib/python3/dist-packages/xdg/Menu.py", line 641, in parse
    menu = self.parse_menu(tree.getroot(), filename)
  File "/usr/lib/python3/dist-packages/xdg/Menu.py", line 659, in parse_menu
    self.parse_node(node, filename, menu)
  File "/usr/lib/python3/dist-packages/xdg/Menu.py", line 668, in parse_node
    menu = self.parse_menu(child, filename)
  File "/usr/lib/python3/dist-packages/xdg/Menu.py", line 659, in parse_menu
    self.parse_node(node, filename, menu)
  File "/usr/lib/python3/dist-packages/xdg/Menu.py", line 691, in parse_node
    parent.Rules.append(self.parse_rule(child))
  File "/usr/lib/python3/dist-packages/xdg/Menu.py", line 768, in parse_rule
    return Rule(type, tree)
  File "/usr/lib/python3/dist-packages/xdg/Menu.py", line 421, in __init__
    self.code = compile(self.expression, '<compiled-menu-rule>', 'eval')
ValueError: Name node can't be used with 'True' constant

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Error processing handshake callback <function get_client_app.<locals>.handshake_complete at 0x7ff627673550>
Traceback (most recent call last):
  File "/usr/lib/python3/dist-packages/xpra/client/ui_client_base.py", line 476, in handshake_complete
    cb(*args)
  File "/usr/lib/python3/dist-packages/xpra/scripts/main.py", line 1632, in handshake_complete
    log.info("Attached to %s", conn.target)
AttributeError: 'NoneType' object has no attribute 'target'

...

Error: cannot access the list of printers
 failed to connect to server
Warning: server connection failure:
 server error
 error accepting new connection