Trying to launch xlogo in xpra via the system service

basic

$ xpra start --start=xlogo --start-via-proxy=yes
2018-01-04 22:39:09,965 server failure: disconnected before the session could be established
2018-01-04 22:39:09,966 server requested disconnect: server error (error accepting new connection)
2018-01-04 22:39:09,971 Error: printing disabled:
2018-01-04 22:39:09,971  No module named cups
xpra initialization error:
 failed to start-via-proxy: unknown general failure
 
$ sudo journalctl -xef -u xpra
Jan 04 22:39:09 nanomachine xpra[17604]: New unix-domain connection received on /run/xpra/system
Jan 04 22:39:09 nanomachine xpra[17604]: server error processing new connection from Protocol(unix-domain socket:/run/xpra/system): need more than 3 values to unpack
Jan 04 22:39:09 nanomachine xpra[17604]: Traceback (most recent call last):
Jan 04 22:39:09 nanomachine xpra[17604]:   File "/usr/lib/python2.7/dist-packages/xpra/server/server_core.py", line 1471, in call_hello_oked
Jan 04 22:39:09 nanomachine xpra[17604]:     self.hello_oked(proto, packet, c, auth_caps)
Jan 04 22:39:09 nanomachine xpra[17604]:   File "/usr/lib/python2.7/dist-packages/xpra/server/proxy/proxy_server.py", line 181, in hello_oked
Jan 04 22:39:09 nanomachine xpra[17604]:     self.proxy_auth(proto, c, auth_caps)
Jan 04 22:39:09 nanomachine xpra[17604]:   File "/usr/lib/python2.7/dist-packages/xpra/server/proxy/proxy_server.py", line 216, in proxy_auth
Jan 04 22:39:09 nanomachine xpra[17604]:     self.proxy_session(client_proto, c, auth_caps, sessions)
Jan 04 22:39:09 nanomachine xpra[17604]:   File "/usr/lib/python2.7/dist-packages/xpra/server/proxy/proxy_server.py", line 222, in proxy_session
Jan 04 22:39:09 nanomachine xpra[17604]:     uid, gid, displays, env_options, session_options = sessions
Jan 04 22:39:09 nanomachine xpra[17604]: ValueError: need more than 3 values to unpack
Jan 04 22:39:09 nanomachine xpra[17604]: Disconnecting client Protocol(unix-domain socket:/run/xpra/system):
Jan 04 22:39:09 nanomachine xpra[17604]:  server error (error accepting new connection)

$ sudo systemctl status xpra.service
● xpra.service - Xpra System Server
   Loaded: loaded (/lib/systemd/system/xpra.service; disabled; vendor preset: enabled)
   Active: active (running) since Thu 2018-01-04 22:32:52 EST; 10min ago
     Docs: https://xpra.org/trac/wiki/Service
           man:xpra
 Main PID: 17604 (xpra)
    Tasks: 1 (limit: 4915)
      CPU: 1.145s
   CGroup: /system.slice/xpra.service
           └─17604 /usr/bin/python /usr/bin/xpra proxy :14500 --daemon=no --tcp-auth=sys --ssl-cert=/etc/xpra/ssl-cert.pem --ssl=on --bind=none --auth=peercred --socket-

ssl

$ xpra start ssl://127.0.0.1:14500 --start=xlogo --start-via-proxy=yes --ssl-key=/etc/xpra/ssl-cert.pem --ssl-client-verify-mode=none --ssl-server-verify-mode=none
2018-01-04 23:31:05,536 Xpra gtk2 client version 2.3-r17863 64-bit
2018-01-04 23:31:05,536  running on Linux Debian unstable sid
2018-01-04 23:31:05,537 Warning: failed to import opencv:
2018-01-04 23:31:05,537  No module named cv2
2018-01-04 23:31:05,537  webcam forwarding is disabled
2018-01-04 23:31:06,755 GStreamer version 1.12.4 for Python 2.7.13 64-bit
2018-01-04 23:31:07,024 No OpenGL_accelerate module loaded: No module named OpenGL_accelerate
2018-01-04 23:31:07,206 Warning: OpenGL windows will be clamped to the maximum texture size 4096x4096
2018-01-04 23:31:07,206  for OpenGL 3.0 renderer 'Mesa DRI Intel(R) HD Graphics 530 (Skylake GT2)'
2018-01-04 23:31:07,224 OpenGL enabled with Mesa DRI Intel(R) HD Graphics 530 (Skylake GT2)
2018-01-04 23:31:07,512  keyboard settings: rules=evdev, model=pc105, layout=us
2018-01-04 23:31:07,514  desktop size is 3840x2160 with 1 screen:
2018-01-04 23:31:07,515   :0.0 (1016x571 mm - DPI: 96x96)
2018-01-04 23:31:07,515     monitor 1 (607x345 mm - DPI: 160x159)
Please enter the password for ssl server 127.0.0.1:14500 :
2018-01-04 23:31:10,984  keyboard settings: rules=evdev, model=pc105, layout=us
2018-01-04 23:31:10,986  desktop size is 3840x2160 with 1 screen:
2018-01-04 23:31:10,986   :0.0 (1016x571 mm - DPI: 96x96)
2018-01-04 23:31:10,986     monitor 1 (607x345 mm - DPI: 160x159)
2018-01-04 23:31:11,495 server failure: disconnected before the session could be established
2018-01-04 23:31:11,495 server requested disconnect: server error (error accepting new connection)
2018-01-04 23:31:11,497 Error: printing disabled:
2018-01-04 23:31:11,497  No module named cups
2018-01-04 23:31:11,505 Connection lost

$ sudo journalctl -xef -u xpra
Jan 04 23:37:41 nanomachine xpra[17604]: New ssl connection received from ::ffff:127.0.0.1, 38042, 0, 0 on :::14500
Jan 04 23:37:41 nanomachine xpra[17604]: Authentication required by PAM authenticator module 1
Jan 04 23:37:41 nanomachine xpra[17604]:  sending challenge for username 'rektide' using xor digest
Jan 04 23:31:11 nanomachine xpra[17604]: server error processing new connection from Protocol(ssl socket: ::ffff:127.0.0.1, 14500, 0, 0 <- ::ffff:127.0.0.1, 37944, 0, 0): need more than 3 values to unpack
Jan 04 23:31:11 nanomachine xpra[17604]: Traceback (most recent call last):
Jan 04 23:31:11 nanomachine xpra[17604]:   File "/usr/lib/python2.7/dist-packages/xpra/server/server_core.py", line 1471, in call_hello_oked
Jan 04 23:31:11 nanomachine xpra[17604]:     self.hello_oked(proto, packet, c, auth_caps)
Jan 04 23:31:11 nanomachine xpra[17604]:   File "/usr/lib/python2.7/dist-packages/xpra/server/proxy/proxy_server.py", line 181, in hello_oked
Jan 04 23:31:11 nanomachine xpra[17604]:     self.proxy_auth(proto, c, auth_caps)
Jan 04 23:31:11 nanomachine xpra[17604]:   File "/usr/lib/python2.7/dist-packages/xpra/server/proxy/proxy_server.py", line 216, in proxy_auth
Jan 04 23:31:11 nanomachine xpra[17604]:     self.proxy_session(client_proto, c, auth_caps, sessions)
Jan 04 23:31:11 nanomachine xpra[17604]:   File "/usr/lib/python2.7/dist-packages/xpra/server/proxy/proxy_server.py", line 222, in proxy_session
Jan 04 23:31:11 nanomachine xpra[17604]:     uid, gid, displays, env_options, session_options = sessions
Jan 04 23:31:11 nanomachine xpra[17604]: ValueError: need more than 3 values to unpack
Jan 04 23:31:11 nanomachine xpra[17604]: Disconnecting client Protocol(ssl socket: ::ffff:127.0.0.1, 14500, 0, 0 <- ::ffff:127.0.0.1, 37944, 0, 0):
Jan 04 23:31:11 nanomachine xpra[17604]:  server error (error accepting new connection)